It's been a while since I've been out in those conditions (6 foot chop or 35 kt gusts, but Wetas withstand that stuff well generally in my experience, Bruce Fleming will agree). My reasoning on further consideration is this: the ultimate surface that holds a screw joint is the area of the threads in contact. Screwing into a nut is not actually an advantage over screwing into a backing plate, the plate can't rotate/wiggle loose, but the nut can, and it isn't any thicker. You definitely get over three full threads (the rule of thumb for minimum thread count) with a M5 x 0.8 or a 10-32 screw, the backing plate is about 3 mm thick, about the same as the nuts. Hence, twice as much holding area (4 screws vs 2) leaves me feeling confident. The likelihood that the screw will strip in this context is very low. That happens primarily by cross-threading; a screw correctly inserted into a properly drilled and tapped hole is pretty darn unlikely to do that, particularly once it's held with threadlocker.