The lettering has to be of a certain size too. Letters themselves can be in standard block capitals, carbon-look or with a 3D effect. DVLA sell them like that, so they must presumably be legal.
I've done it to indicators mate, I put them in the oven.. Don't just leave it in there for a certain amount of time like you said earlier, just put them in and keep checking every 30seconds or so until you can peel off the lens.
Its pretty easy actually, much better than the boiling water trick which steams up the lenses a treat haha
I think it would finish the front end off a treat.. Maybe combined with a VZR or 2slat grill.
Joe