My wife's shiny red Brompton arrived today. The bike rides beautifully. It is in very clean condition, with a nice clickety-clickety Sachs 3-speed hub offering a fairly wide gear range.
There's no minimum insertion point marked on the (31.8mm Ø) seat-post, which is about 50cm long (not counting the narrow section at the seat end) and there's about 9cm of post inside the seat-tube when the post is lifted out to its maximum extension and the flared end catches. Will that insertion depth do?
I think the design prevents you from exceeding this. The bottom of the seat tube is widened slightly, and you can extend it to it's maximum allowable point without problem. It's a great idea from them.
yes, very handy if the highest posture is exactly what you need (the little adjusting can be made at the saddleclamp) and also it prevents seatpost theft. If I would not need the highest position I would probably cut the post and widen the end again to get it such comfortable when folding.
And jagatron, yes, the flared end on the seat-post is a good idea. The bike seems so well thought-out, I was almost certain that was its primary purpose, and did take the bike for a ginger spin as soon as it arrived. But I feel better having the corroboration
I ride at full extension on the regular length seat post and never a problem. The best part is I don't have to reckon with position to get it just right, as I have to on the extended post fitted on another Brompton, I just lift it all the way and I'm ready to go.