Nice progress Rein!
Can't wait to see it in the air.
I meanwhile ordered some Skytex 32 hard and 27 at Extremtextil
for the bespoken 9m v2 and a 6m later for foiling. (Already built a foilboard )
Parallel on the 12m I got most issues sorted like turning ability by shortening lines, making a wider bar (70cm) and attaching the outer Z bridles at the TE directly as well as tightening the outside Z bridles.
At low wind speeds I still get a bit of backstall in the beginning, the reason is most likely the upper skin shape on the LE as the transversal shaping (3d Seams) are a bit too much and the billow by manual measures doesn't taper off to zero. So the LE is a bit bulky and the flow can't follow the billow shape so well at low RE .
The billow shaping is improved by not doing it manually by tensioning the straps this time but with Surfplan.
I hope this better panel shaping and less backstall will increase the low end for kite boarding a bit. For leisure foiling, snowkiting and buggy it doesn't really matter once you have some speed or loop the kite the backstall is not so much anymore with more apparent wind.
Above 15 knots I get nice powered sessions on the 12 and twintip, the upper limit for me as a beginner is around 25knots.