You’re right, my foil seems to be the same that the Redwood one. I’ve bought it cheaper because directly to the factory via Aliexpress.
I’ve fixed the foil directly on the board with 4 inox bolts:
Bolts are sealed into epoxy resin + microballons. I’ve used a PVC pipe (32mm) to prevent that the resin polymerization melt polystyrene of the foam. Also I’ve filled it in several times (need some days).
That seems very robust, I’ve ride it severals times with my kite: no problem.