I never really liked the Idea of self tappers either.
Although sailboards all seem to have them and without any issues.and there are a lot of really old sailboards around so they should know.
From my experience if you do happen to strip one out you can allways re tap it with a larger screw.This seems to work well.The inserts are normally quite solid blocks of plastic, so you can just screw a larger screw in and you will have tight fit again.
Best thing is not to take the foot straps on and off all the time.
So dont go sharering ya board around with your goofy footed mates! (This is how some inserts on a board of mine started to go)
They should not work loose though unless you have been taking your straps on and off all the time.
Sheil be right

Enjoy your new board!
regards
Luke