what is the preferred way to hold a wingbolt to the ply support? A blind nut, or threading the ply? The ply support is 1/4" and for the bolt I was planning to use a 1/4 bolt. The plane is a .60 warbird.. thanks

Most kits just drill and tap the ply plate and use a nylon 1/4 bolt. It works just fine as long as you harden the threads with thin CA. If you are using a metal bolt, I would use a blind nut.

+1 on just threading the ply. Threads hardened with thin CA then retapped are probably as strong as a blind nut or a brass thread insert.

I always drill and tap hardwood mounting blocks, but use blind nuts in plywood. If you are using birch plywood, then you are probably fine with drill and tap too, but if you are using poplar "light ply", then I would definitely use a blind nut.

Thanks. I guess ARF's mostly use blind nuts because they are faster to install...