I'm quite enjoying my new RT-58, it's notably more comfy than my ally Trek in terms of road 'buzz'. That said, I was thinking of replacing the supplied ally seatpost with a carbon one. Ideally this would be a Specialized CGR for maximum comfort, but they only do it in a 27.6mm diameter post, and the one on the RT-58 is a 31.6mm. So, can I, and indeed should I, shim the post to fit? Or should I buy something else like an Easton EC90?