I'd recomend 7-9 for regular sets if you aren't also trying to save time. Tho it looks like this MK legal ruleset is leaning towards less than 9 stages. You guys definitely would need to do something about DSR for finals matches if you go with 1 stock AND a conservative stagelist.
Another idea might be to have as little as 2 games with the an added "must win by 2 games" clause. So you can't win 5-4, it has to be 6-4. Standard in Tennis and I think it fits 1 stock matches perfectly.
[collapse=Taken from wikipedia]In standard play, scoring beyond a "deuce" score, in which both players have scored three points each, requires that one player must win two consecutive points in order to win the game. This type of tennis scoring is known as "advantage scoring" (or "ads"). In this type of scoring, the player who wins the next point after deuce is said to have the advantage. If the player with advantage loses the next point, the score is again deuce, since the score is tied. If the player with the advantage wins the next point, that player has won the game, since the player now leads by two points. When the server is the player with the advantage, the score may be stated by him before the next point as "advantage in." When the server's opponent has the advantage, the server may state the score as "advantage out." These phrases are sometimes shortened to "ad in" and "ad out." Alternatively, the server may simply use players' names; in professional tournaments the umpire announces the score in this format (e.g., "advantage McEnroe" or "advantage Borg"). [/collapse]
What I'm thinking is:
-each set must be at least 3 games, 5 for finals sets (still time to adapt and bring a set back when losing 2-0)
-you must beat your opponent on one of his CPs to win, no winning on the "neutral" and then only your CPs (defeat them when they have an advantage)
-if you stagelist winds up being too small, modify DSR to only apply to the 2 or 3 most recent CPs. (stage diversity, close sets may require skills to be tested on every stage)
Small possibility of sets lasting "forever" against 2 evenly matches opponents. It might be necessary to cap the amount of games somewhere around 13-17. This isn't as absurdly high as it sounds. 17x3= 51 Minutes and I saw a 9 game set of regular brawl doubles last longer than that just this saturday.