I've used the NSI surface mount inserts a couple of times (http://xtremebigair.com/NSI-Surface-Mount-Footstrap-Inserts-P906.aspx
), where I had to test a new footstrap position, and it worked really great !
Extremely strong and lasted for the months used, but I would not "depend" on it in the long run
But I might be surprised
I am just a bit sceptical that you say you " keep going through them" about production boards I assume ?
So taking a surfboard might be low cost, but wont you go through these at a pace 10 times faster then ?
I would not use much effort on mounting plugs, if they (the boards) only last shortly - but maybe try the deckpads linked by NorCalNomad.
These deckpads with integrated footstraps look like they will hold even better than the NSI ones, although I dont know havent tried....
Although, not that inexpensive then ?
On the other hand, if it is easy for you to mount plugs, it could be the simple solution.
Regarding footstrap position, you might know, but for others:
Remember that the front strap should typically be mounted just slightly more aft than where your front foot is strapless, as you have more control and can go faster in chop both out and down the waves, and still maintain the same glide.
Just a hint