Could be possible, but not for the 1st series. All Reyn. 531 pg seat tubes take 26.4mm seat posts. You must be talking about 1990's 525 frames.
I am, like I said in my post? ;)
@Björn started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
I am, like I said in my post? ;)