thanks for all the input. given all that, i think i'll start with some emery cloth and keep removable to a minimum. i have read .1-.2mm difference in diameter isn't a big deal. otoh, i do have a couple of other 26.4 posts from mtb's. they're just black and i'd have to cut the length down. and, they aren't original, of course

the current post insertion leaves probably 90mm exposed. iow's, wall strength and material removal i don't believe would be much of the concern. but, like ya'll said it's the seat lug issue. i'll see how it goes!