I have an unmarked sorta uban/mountainy frame - unbranded and no seatpost or other measurements stamped - and was going to try to figure out the seatpost diameter somehow. Bored, today I decided to throw on my 27.2 post and clamp from my Felt - voila! it seems to work, so at first I thought, great, its a 27.2. But, now I'm thinking that a post that was one or two sizes too small would work if the clamp held the tube together tight enough. So.... how tight should a seatpost fit into the frame before one puts on the clamp. I mean, this slid all the way down to the seat, but with the clamp on it holds fine even with my weight on it. Also, if 27.2 is too small, what are the consequences of riding on this?