A plumber installed a Delta shower faucet for me today, to replace one that was leaking and corroded. I'm guessing that unsightly gap between the back of the handle the rest of the assembly are within spec. I'm guessing it's a function of the old rough-in valve position relative to the wall. Maybe there's an extension piece--whatever that tube is called--that would reduce that gap? I don't actually recall what the old one looked like, I'm guessing the same.