It's an old Japanese frame, had a non-stock 26.8 seatpost installed. Way too tight, I needed to twist it out with a pipe wrench. However, the seat tube and compression cut wasn't deformed, just over-tight at 26.8.

Would it be safe to replace with a 26.4, or perhaps down to a 26.2? Not clear on how much difference .4 actually makes in a seatpost fit.

Thanks.