I decided to try to get rid of the protruding “clamping screws” that I showed earlier…
…so I got yet another “folding bike stem” from aliexpress - and this time I got one in 28,6mm diameter 
It is supposed to clamp a 25,4mm handlebar… but used in reverse clamping a 25,4mm seat post in combination with an Ergotec High Charisma makes for an even better setup as there are no protruding “clamping screws” occasionally touching my tights/pants.
