NB Problem Solvers

you can take apart that saddle clamping hardware and / or saw off the end of the tubing square
or maybe even just turn it over the other end is probably cut off square

shim the ID of your seat post tube to take a common sized seat post as there is being shown .. ^^above^^

Or have a tube, the same size, made and welded up to get the pushed ahead saddle mount you desire ..




Father was a machinist .. so making rather than internet shopping seems better..

welding on a 7/8" diameter tube Horizontal on top and buying one of Brompton's excellent Penta clip saddle clips
which is stepless, secure and works in 360 degrees will have your saddle positioned above the horizontal tube.

Then the saddle set back adjustment range can be user chosen..
Idea, modeled after Brompton's own Saddle adapter pin..

Which offers the horizontal tube when fitted to a post, which also has a 7/8" top diameter

As most tube seat posts do.