Please tell me the double nut is for mock-up only...

You need positive retention hardware for this stuff Nick. That means self retaining bolts, castellated nuts with cotter pins, and safety wire. Otherwise I would make sure your life insurance is paid up so the wife and kids have something after you're gone.

Helo's do one thing better than vertical take offs - they vibrate like you would not believe. Loctite ain't gonna cut it on this one.