Hey Bletti, pretty interesting info there about not using any further supports.
There is a 2nd hand shinnster on buy/sell too.
I recall one of the brands (TKF?) saying that the mast only takes on 300ml so probably not a huge difference flotationwise.
They leave them open so you can empty & rinse, so you're right you'd have to hope there was no leaks if you sealed it...
You're probably right about the extra weight not making a huge difference - I'd imagine the biggest load by far would be hitting bottom at full speed with feet in straps.
You could also PM Jasonwave and ask how his is going?
I agree with what you and Dusta have said re boards. I've been reading a lot of translated french forums recently, and that's really confirmed to me that of the cheapies they rate Zeeko or Alpinefoil far above the others for ride & build quality.
I'm waiting for an updated quote and some questions answered from Alpinefoil - but currently I'm liking the fact that they've hit 33kts with the 'sport' wing on the Aluminium foil - so the upgrade path if you feel the need for speed is just one additional wing purchase. Plus their carbon masts & fuse can both be used interchangeably and purchased separately - so can update piecemeal later on, if really addicted.