Title says it all I think. I have a 30.9 seat post and a frame that takes a 31.6. Does that 0.7mm matter? I dont see as anyone making a shim that small... does it hurt anything to just crank down the collar a little more? Should I cut a strip of aluminum flashing and stick it in there? couple wraps of tin foil? Im thinking as I type so I may be spurting stupid ideas. But any and all opinions are welcome.