What solved this problem for me was attaching the wrist leash to my upper arm. No problems tacking or gybing now

Watching Travis video gives a clue. He keeps both of his hands down, below his head. You probably have your hand straight above the head, and perhaps a longer line. If your hand gets pushed behind your head, I can see how a longer line could catch the helmet. Bending the arm would make it more likely.

gregwho said..
.. with larger sails if I don't put the sail above my head while rotating it, it's wingtip would surely hit the water.

In the clip above the wing is actually plenty above my head, it's just the camera angle that is not the most helpful. I think the more important bit was keeping both hands extended, and in front of you. But with bigger wings in light winds some different technique is needed for sure.

Here are a few examples with a bigger wing (6.0) in very light winds. Maybe you'll find some tips from here, or perhaps with the 7 and 8 m2 wings it's totally different?

At 01:14, 01:53, and 02:35

@Taavi seems like having an orange wing and a blue board is way better than having a blue wing and an orange board ;)