ORIGINAL: Sport_Pilot
You are refering to blind nuts. Don't use them, the tapped wood holes work fine. In fact better than blind nuts. Metal blind nuts will eventually wear the threads off the nylon bolt, in fact it will strip them off if you cross thread them. The wood hole is not as likely to do this.
As a carpenter by trade, with all due respect, I can't say I agree with this statement. I see nothing wrong with blind nuts, and cross threading causes damage no matter how you look at it. In the case of a blind nut, the damage would be to the softer bolt. Easy to replace. In the wood, it would be to the softer wood. Not repairable ( in a practical sense) and a blind nut or metal insert would be the solution anyway.
As far as wear goes, I have never, in over 40 years, worn out the threads on a nylon bolt, talking them in and out a few times a month, even over several seasons. I loose them before that ever happens.
That being said, IMO, either way of mounting a wing is perfectly fine. I use both wood (for 60 size and smaller) and metal blind nuts (for over 60 size to giant scale, and for the latter I use metal bolts as well). Never lost a wing yet. (from wings bolts failing, that is).