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.