i hear aaron ross is about your size and he does 720 like there nothing... but he is also aaron ross.
Aaron Ross is nowhere near that size (I've ridden with him twice).
Listen dude, there is no such thing as too big (unless you're 500lbs). Get a 22" top tube, Grand Slams, 180mm cranks and ride your bike. Trust me, I'm 6'3" 280lbs.