Ive run into a snag mounting a Fugi 43 onto my Cap 21 maybe someone can advise me Ive always used Tnuts for mounting but the mounting box is made is such a way
with reinforcing triangle stock that the t nuts wont fithonestly the only way I can see doingthis is to use 10/24 threaded inserts -my gut tellls me it will be ok but id like to hear what more experienced builders say thanksthe box is pretty meatyalmost 5/16 thick

You can simply use a long 10-32 bolts, fender washer, and nylon lock nut if you desire. There's no rule that states a blind nut or threaded insert is required. It only has to be secure.

Don't use inserts with an engine that size and a firwall that thin. Make up a 3/8 inch, or better yet, a 1/2 inch plywood motor mount using the aircraft grade plywood you can at the hobby shops. Oversize it 1/2 inch all around the motor box. Use T nuts to mount your engine. Epoxy and screw this to the motor box. Epoxy hardwood triangle around the perimeter of the motor box. If the motor box is finished, sand it off with 100 grit sandpaper. Use three hour epoxy for all of this. If you don't want to add the extra length to the motor box you can cut back the existing box the thickness of the plywood you are using and use the same process. Dan.

Tired old man is right.

Thanks guys im considering aanother methos have you heard of this -threaded inserst but with a 1/8 inch front plate to cover over the inserts with precisely drilled holes
only big enuff for screws to pass thruin effect making T nuts out of thredaed inserts-??? its just so damm impossible to get behind to put in any nuts

nutserts will rip out, guaranteed.

Can you post a picture? you might be better off cutting access holes in the engine box or threading a long bolt through a fender washer, through the firewall from behind, through the engine, then put the nut on the forward side, and cut off the excess bolt length.

Thanks all im shying away from inserts will rexamine maybe i can cutopen the box in the fuse enough to get in there