It’s cold outside and I don’t want to go out to the garage. Now I can fit a 27.2mm but it’s tight, probably due to corrosion Maybe a 27mm would be better.
I've just checked my '92 Pantera again and it's 27.0.
It came with a 26.8 seatpost fitted but it kept sliding down, so I bought another seatpost which is 27.0 and it hasn't given me any problems since.