Hello all knowing mod people

A friend of mine has an epiphone sg special


(yes the one that comes in with the starter pack) and he has a piece of diamond plate and wants to make a pickguard out of it, so it should like like this:


But he doesn't want to buy that since he says it doesn't fit his model, his diamond plate is about 2mm thick.

So we have a couple of questions.

First of all, how thick should it be so he can screw it on top? Second of all, we wanted to know if doing such a thing would suck tone on his guitar.
I would keep it 2 mil and tone will remain the same. But i've never used an sg before and never replaced a pick gaurd, sooo

Epiphone Les Paul Standard.
Squire Strat.
Marshall AVT100 2000.
Ibanez Tube Screamer.
Electro Harmonix Metal Muff.
Boss Tuner.
Boss Chorus Ensemble.
Jim Dunlop Crybaby.
it wouldnt suck tone to my knowledge...2mm is pretty nicely balanced

if you have the tools and knowledge to cut it out and shape it...go for it..