So here's the issue. I'm a small guy, about 5 feet 4.5" which would, by all usual accounts, put me on a 49 or 50cm c-t seat tube. right? But i've taken my inseam measuments and my standover is just shy of 28 inches. Yes, from attempting to get into cycling i have discovered that i have freakishly short legs and a long torso.

I read that for 700c wheels, the minumum standover is 30 inches. I'd imagine that holds true no matter what the size of the frame? So do i defintely have to go with 650c wheels? Is there any way to avoid a sloping top tube? My torso is proportionally a good deal longer than normal given my height/inseam numbers so what kind of numbers should i really be looking for? Like a 48 c-t seat tube and 51/52 c-t top? Any suggestions for a good used bike ($600 - $800 range) that comes in that kind of size?

Any help would be greatly appreciated. Thanks!