Strangely enough I have covered my Zagi's top side in yellow too. BUT I don't know how long it will stay yellow. The tape I think is old and not sticking too well. Tape is quite thin too compared to my other colours from Johnson Tapes
I've seen then flying on the slopes. They fly fine. Compared to the Zagi (subject of this thread) they have a much lower wing loading which means they will fly much better than a Zagi in light winds, but will need ballast if you try to fly it in 25mph+ winds. And the Zagi is covered in cross weave tape which makes it almost indestructible, which the Xeno is not.