This isn't an 'answer', but a follow-up question:

So this mod (the transparent back for iPhone 4S) would technically invalidate the Apple warrantee, correct?

(I mean, I realize you might be able to fool them if done correctly, but what would Apple say if you had an unrelated problem that would normally be covered by the factory warrantee? Do you think Apple would use this as an excuse to not cover repair/replacement?)

I already purchased my replacement, but I'm wondering if I should wait till the warrantee runs out.

Thanks!