I forgot about Gerber mask, but I've only used that on a non angled orientation (flat graphic stencils), and I think that is the real issue at hand. I'd almost recommend instead of camming the edges and painting them, cut your vinyl 1/16" smaller than your face, and then plot mask 1/8" smaller than the face. This way when your remove the mask you have paint over the edges of the vinyl. It does diminish the effect, the cam looks sharp, but since you are shooting at a 45deg angle to your mask, you're going to fill the void at the edge of the letter.
Just a thought, are these laying face up or face down when you shoot them?
BTW, I think your stuff is awesome, I wish I could find customers that want a superior product as opposed to a cheap one.