I can top level 9s, but, I wouldn't know how far to determine outside of the level 9 box. I love setting the auto-handicap against small free for all matches (stock 3 matches). In brawl, the handicap works by, 1st place gets +20% damage at the start of match, while the last place loses 10% (0 being the lowest possible). Meaning, the more you win, the more damage you accumulate at the start of matches. I like to see how high I can get. It gets really annoying when you start off at 100% or higher, cause then, if I die, I come back with that same percentage, so it becomes a dodging game. It's mad fun though, I recommend it for all in brawl and melee (though melee's set-up is different.
By the way, I hate lv 9 pikachu's in brawl. Never seen so many standard Bs and down Bs used before. Same with fox, always spaming the standard B to use that laser, and steal kills in time matches.