Detroit are a jump shooting team that lacks a deep interior presence and lacks slashers. They're not going to take advantage of the C's being in the penalty ...... unless Boston make silly fouls.
Play with your heads, you're in the penalty, don't reach in as often. This is a good FT shooting team that struggles to score in the halfcourt against the Celtics. Don't give them easy points. No reaching, gambling, overzealous defending. Just keep it tight, show the refs your hands and move your feet. No need to give away unneccessary easy points for the rest of the half.