I have just finished my vortex. Final efect is pretty cool:
Materials - 30g ripstop polyester + Dacron
Frame - LE P2X+P300; LS 5PT; SP,US 6mm CFT
Still not sure about bidle - inhaul should be 65cm with towpoint 5cm back for turbo or 70cm with 5cm back for turbo.
Many thanks for Christian for sharing the plans!!