Pal Nuts
I'm surprised nobody has responded, so I'll chime in.
A pal nut against a lock nut would certainly be a belt and suspenders approach. I like to think outside the box but frankly this seems like a overly redundant redundant idea to me. I think you would be better off putting your effort towards making certain you have correct thread engagement and keeping your lock nuts tight. If you do those things, there really isn't any purpose in the use of the pal nut.
I know pal nuts were pretty common years ago on the small Continentals but I don't think most overhaulers use them today. Not much of a nut really.