Ah, I see.

You may be right about the frame flex, particularly in regards to the chain keeper rub. I tend to think that when it comes to the lack of responsiveness under pedal input, however, that the tiny rear triangle and short stays are probably not flexing, and that the cranks are at fault in that case.

that said, I'm not an engineer, and you may be right. Since I'm not averse to putting some money int this bike, good process suggsts that I go after the obvious, low hanging fruit, and there's no doubt in my mind that the crank and chainring are flexy, and that pedaling would feel better if they weren't.

I think one of those $50 Lasco cranks that are often indicated for fixies would be stiffer than the stock Dahon crank, so if I can find one in the appropriate 170 length, I'll probably throw down for one of those and see. I'd try a Litepro as posted earlier, but I really just want silver.

oh, and yes, no doubt changing pedals would help, too; considering some MKS quick release types