There was a windsurfing footstrap manufacturer a while ago that made break away foot straps (Footsavers I think they were called). Basically all it was they had an extra piece of Velcro that went between the overlapping Velcro pieces that hold the two halves of the strap together. This extra piece of Velcro "neutralized" a portion of the other Velcro so there was less force holding the two halves of the strap together. You custom tailored the holding power to your liking by increasing or decreasing the amount of overlap of this "extra" piece of Velcro. There's no reason you couldn't do the same thing on most foot straps made today.

Another possible solution would be to use a break-away screw to mount the strap to the boat. A nylon screw would have much less holding power than the stainless machine screws normally used.

I don't really understand the rationale of using only one foot strap. I've windsurfed for almost two decades and the only time I've ever had any concern using the straps is when one foot pops out and the other stays in. The potential for foot and knee injury goes way up when one foot is planted and the other is unrestrained. Seems to me that having two foot straps mounted on the hull would go a long way towards improving safety and giving a more secure ride for the crew.

sm