So I saw this guy riding down by the Flatiron building the other day on a great looking bike. It was a vintage road frame--nothing recognizable--and he was riding it as a fixed or ss conversion, but on 20" wheels. Sounds ridiculous, but something about it looked really fun. He had upright or riser bars, and it had that streamlined urban rider look, but the smaller wheels made it look even more so.

I was just wondering if I could get input on what kind of work this type of project would involve. I was thinking of taking one of the beater frames I have that aren't worth the money to fix up and experimenting with something like this. I'm well-acquainted with converting road bikes to fixie, but not with working outside of the usual bounds, or hacking.

Obviously, the cranks and bb clearance will become an issue, but it looked like this guy was riding a taller frame, which I think compensated for this.

Anyone have ideas on where to start? How much of a drop in bb height and tt height am I going to hae to calculate with the change in wheel diameter? If I normally ride a 53/54cm (21") frame, what size frame would I want to use for such a project?

Please don't tell me the idea's idiotic. This is something in the spirit of fun and creativity, and even if it doesn't turn out great, I'd rather learn from doing it than being told not to.