I wouldn't worry too much about trying to match the seatpost dimension. Just buy a replacement Spaceliner seatpost on eBay... they come up for sale all the time.Anyone know what the seatpost size is on these? My caliper gets 20.8 if i measure mine. Do they make 21mm seatposts or 20.5? Ive got a frameset with a stuck post and i am likely doing to need a replacment once i get this one out.