Seatpost stopper for Brompton

###logfile
2018-06-24: v0.0
2018-06-27: v0.0 printed, it worked out-of-the box...
2025-07-25: added a comment

###at a glance
* for inner diameter 29.2 mm, simply scale diameter if necessary.
* features an M5 hexnut slot (= 8mm width)
* hole suitable for a regular M5 allen screw head.

###summary:

This is a simple seatpost stopper. Works for seatposts with an inner diameter of 29.2 mm. I designed it for a titanium seatpost which didn't feature a flange.
I didn't build it from scratch...most of