Just a quick one here...

I'm working on my new Tarmac and purchased a zero setback Thomson seat post. I have the exact same post on my roubaix and I figured that since they both have the same seat tube angle that the post would be fine on the Tarmac. I guess they must round the seat tube angles because they are not exactly the same. It seems like the Tarmac is a bit steeper and therefore the seat post clamp is sitting farther forward on the rails then I like.

Asthetically speaking I'm sure I should use a set back post, but is there a true issue structurally. Bear in mind I'm a lightweight at a paltry 145lbs.

Have a look at the photo and tell me what you think...