Asking from the challenger to win by 10-8 or better is just not fair. In unlimited match there just can't be any draw odds.

Euwe proposed a compromise solution: unlimited match to 10 wins, but in case of 9 wins to 9 wins the match goes in 10 games overtime. In case overtime ends in 5-5 tie, the champion keeps the title. That way both was possible - unlimited match and draw odds for the champion.

Like always, Fischer rejected everything that wasn't exactly how he wanted.

> In the 1910 championship match between Lasker and Schlechter, which was schedules for only 10 games (like nowadays :-)), "...the challenger had to gain an advantage of 2 points" and if it ended in a 5 1/2-4 1/2 match in favor of Schlechter, it would be declared a draw (My Great Predecessors I pg. 173).

And again Kasparov states something as a fact, but in reality nobody knows what the conditions were. It might be true, but it also my not be true.

In my opinion there should be somekind of champions advanatage and in best of 24 format, a 12-12 draw odds were reasonable. Draw odds and rematch was not. With unlimited match, there just can't be any draw odds (2 wins advantage is just to much), so the rematch is almost only  option for champions advantage. In 1978, 1981 and 1984 Karpov had absolutely no advantage in the match itself, but of course he had a rematch right.

>In the 1910 championship match between Lasker and Schlechter, which was schedules for only 10 games (like nowadays :-)), "...the challenger had to gain an advantage of 2 points" and if it ended in a 5 1/2-4 1/2 match in favor of Schlechter, it would be declared a draw (My Great Predecessors I pg. 173).

Chess historians disagree here. [And in any case, MGP is not a historical source :)]. Wikipedia page
My own opinion is that the 2-pt edge idea is a myth that has simply been copied from one source to another (Kasparov is well-known for his trumpeting of this idea, in conjunction with him being the only champion to defend via winning the final game [Seville 1987]). To the best of my knowledge, there is no primary evidence in favour it (usually, a "secret contract" is mentioned, though this is hypothetical -- I should think any such "secret contract" would be more likely to involve a re-match).

As usual, the man-on-the-spot is Winter (#4144), quoting Preiswerk, 10 days after the match ended (and thus the primary source, though still perhaps mistaken or misleading): A narrow victory by Schlechter would by no means have given him the world championship but, instead, it would have brought him a serious return match to be carried out irrespective of its financing. This may not have suited the two masters, who, after all, are also excellent businessmen. Buckley even wrote (in the American Chess Bulletin, at the time) that Lasker would still have been titular champion (in some sense) had Schlechter won all the games.

Additionally, Lasker's correspondence at the time (two days before the final game, written for the New York Evening Post) also suggests that Schlechter would gain the title by 1-0. The innuendo of Preiswerk seems to be that a 2-0 win by Schlechter would be more likely to obtain funding for a "true" match (the 1910 match was underfunded, which is one reason for its shortness). So it might be more proper to say Lasker really had a re-match clause here. [And to be pedantic, this is not an example "of an unlimited match to 6 or 10 games"].

>In 1911 Capablanca challenged Lasker and these were the champion's conditions: "the winner was to be the first to win 6 games, draws not counting, but with a limit of 30 games; after the 30th game the match was to terminate and the winner would be the player who had a lead of not less than two points, while with an advantage of one point the match would be considered drawn"

Capablanca's original challenge was of 10 games up. Lasker responded with 6 wins, or best score by at least 2 after 30 games. Thus, (and I don't have the original conditions in front of me), it seems that 6-5 would be a win, but 5-4 with 21 draws would not. This again is a bit different (and makes more sense to me) than 5-5 being a draw in an "unlimited" match. In any case, this was at an early stage in negotiation, not a final agreement. Also under dispute (besides number of wins and length of match) were: location (Lasker didn't want tropical Havana), copyright (Lasker wanted to retain the rights), and time limit (Lasker wanted 12 moves/hour, while Capablanca said 15 --- in fact, in The Chess Amateur, this is the only clause that is noted in their brief blurbs, with Capablanca saying that he would never play at such a time control).

>However a decade later they played to the best of 24 games

The 1921 Capablanca-Lasker match was 8 wins or 24 games (some sources say 30 games, though again Winter, citing the match book, seems more accurate). And Lasker had lesser interest herein, having "resigned" the title to Capablanca in 1920 (though this was not recognised by most).

>Here are some examples from the 20th century of an unlimited match to 6 or 10 games where draw odds were given to the champion (5-5 or 9-9).

The others listed (Bogoljubov-Romanovsky, Levenfish-Botvinnik) are not World Championships. In the former, Bogoljubov had 15/17 while Levenfish was 2nd with 12.5/17 -- for the latter, Levenfish won with 12.5/17, while Botvinnik did not play (finishing his dissertation). Romanovsky was probably lucky even to get a match (which he lost 5-1 -- plus Bogo won their game in the tournament). Krylenko organised the Botvinnik-Levenfish match (whether he "ordered" it to "punish" MB is a different issue), and the purported rules from Capablanca-Alekhine were largely copied.

>Again, it has always been the champion's right to retain the title in the event of a draw. [...] In an unlimited match the only fair draw if playing to 6 wins is 5-5, and the only fair draw if playing to 10 wins is 9-9.

The "wins-only" accounting has the feature that it can neatly cut out the "event of a draw" except for abandonment. I find the phrase "fair draw" in an unlimited match to be a misnomer.

>For those who strongly feel that this 2 point handicap is too much should consider this in light of Karpov and the Soviets reintroducing the champion's right to a rematch---thereby the challenger is forced to defeat the champion 2 different times.  I ask in all fairness, which is the more difficult wall to climb?

This is not exactly true. Firstly, the challenger becomes Champion after winning the first time (see Smyslov and Tal -- and Euwe, though there the re-match was freely granted). Furthermore, and perhaps a bit pedantic, this means that the challenger-now-Champion need only draw the second time around. Also, the question of whether the 2-point handicap is "too much" can be considered in a self-contained manner, and comparing it to a re-match clause seems to conflate the issue. [My personal contention is that the "rematch" clause does well when there are exactly two players who are admittedly in a separate class, but elsewise gives the Champion too large of an edge toward eventual retention. For instance, in the run-up to 1978, Euwe had suggested a re-match only in the case where the challenger had won by the minimal margin of 6-5. Also important with re-matches is the availability of funding.]

>Already in 1963 Fischer had challenged Petrosian to a 10 game match with draws not counting (Profile of a Prodigy pg. 71).

Notably missing from the challenge was a clause that would allow Petrosian to retain the title if the score of 9-9 was reached. Similarly, I don't think that Fischer mentioned such an idea when he proposed 10 wins back in 1971.