Saw a company on the net somewhere that was selling CF posts for Bromptons. Had the necked down top for the Pentaclip,just like the stocker.
I'm not worried about CF just suddenly failing;I know two people that had steel forks suddenly go on them. But in this case,there's too much post sticking out,too little clamping area,and the post is regularly being 'reclamped'. On my road bikes,I set the seatpost height once,tighten the clamp with a torque wrench,then leave it alone.