I hereby accuse my P13-9 (converted to a P15 either in Chicago or at the LBS, before sale) of being 'too flexy'. It has a 25 inch frame, weights 26 or 27 lbs, and boy do i get a lot of chain rub on the front derailleur - the bottom bracket is all over the map even without my standing up on the pedals !!
Luckily, the steamroller wheels (640 gram araya 27" single-walls) track straight down the road, even if the leaden frame is wiggling all over the place !!
- Don Gillies
San Diego, CA, USA