I should have said that I have tried the insert. I found I could never get it quite right, either 5mm too high or 5mm too low. I still have both said inserts so maybe I need to give them another go, but I was wondering if there were other solutions. Is there a Brompton seat post that has markings?
Similar to Sergeant_Pluck for my dad I used hockey tape/adhesive fabric tape - like you'd use to finish your bar wrap. Worked perfectly for him. Until the bike was stolen.
It was on a Ti seatpost, but I can't imagine that made a difference.
I should have said that I have tried the insert. I found I could never get it quite right, either 5mm too high or 5mm too low. I still have both said inserts so maybe I need to give them another go, but I was wondering if there were other solutions. Is there a Brompton seat post that has markings?