2mtr

Will a 26.8 diameter seat post work on my bike, which has a 27.2 hole -- for lack of a better word. Even with a shim, would it work?

I think my bike is too small for me. I'm 6'6", riding a 62 cm surly. Lately, I've been having some soft tissue issues, and got a new saddle, which forced me to sit directly over the seat post. This then causes my arms and neck to ache. Yada Yada Yada, I think I need to move my saddle back. Only way to do this is to get a setback seatpost.
Haven't found many good ones, but most I've found with enough of a setback to make a difference are MTB. Any suggestions on seatposts, or how to take care of this problem would be greatly appreciated. Thanks.

Ya Tu Sabes

If you're feeling handy, you might try the following fix: Get a gooseneck-style BMX post - the kind with a serious backward bend. You'll want to find a post with a diameter narrow enough to fit inside the post that fits your frame. Then cut your original post and put a vertical notch in it. Place the gooseneck inside the old post and secure it with a seatpost collar. You can see a picture of the result here:
https://www.fixedgeargallery.com/2004/michtom20.htm