Well guys, I have decided to ream the seat tube, for a number of reasons. I suspect it isn't a great ream from the factory... My head tube was slightly over reamed... And given that the ream is probably too large as is for my 27mm post, there are way more 27.2mm posts around than 27, and my tubing is not uber thin; I think it just makes sense to go this route

I got a killer deal today on a used-once (for the same purpose) no. 28 Chadwick Trefethen angle blade reamer.

I have watched a bunch of videos, will buy some other tools and supplies and have a go of it sometime this summer.

I'll keep everyone posted! Very nervous but also very excited to do this.