If my seat tube (vitus 172) is 28mm, and it measures at least that for the full length. Does this imply a 26.0 or 26.2mm seat post? Furthermore if i were to run a reamer down it would 26.2 be too much?

Verktyg gave this info some time back: 26.2 or 26.4 depending on year of manufacture.

and... I just realized this question must be related to your newly acquired Motobecane G.T. I also have a Moto G.T., though I believe mine is a '76. My seatpost is 26.2mm.

bingo and thankyou. since i dont have the original post and i am trying to get the hole rounder i am thinking about using the reamer i have until it cleans up. I have done a few of these with a reamer my dad had from way back. Just want to be conservative enough that i dont wreck the seat tube.

i got my adjustable reamer from my exwifes house. She doesnt seem to need it. Anyway i attempted to make the hole round again as i approached 26.2. It was close but since i have an unused laprade 26.4 i decided to go for the gusto and get to 26.4. It worked and is a real close fit. Better than most any other bike i have.
i hope this doesnt confuse the next guy that gets this bike.