Pardon the top-posting. James, I use 1/4" diameter sheet metal screws. If the holes in the faceplate are too small, drill them out. While you are at it, countersink the face side of the faceplate so that the wood that is lifted by the screw has a space to go into. That way the faceplate always sits flat on the blank.
Normally, I use 1 1/2" long screws, which on my faceplates lets about 1" of the screw project into the wood. Unless the wood is particularly hard, I do not drill pilot holes. 90% of the pieces I turn are wet, so there is not need to pre-drill. I simply screw them in with a cordless drill. For smaller pieces, occasionally I use 5/16" nuts as 'washers'. I always use as many screws as I can, usually about 8 or more. It has been many years since I had a piece come loose.
I have turned hollow vessels up to 12" in diameter x 20" deep, using a 3
1/2" diameter faceplate. In order to do this, I always use the live center as a support, then use a steady rest to hollow the piece. As long as you don't allow the piece to 'lever' against the faceplate, this is perfectly safe.Incidentally, all my faceplates are homemade, of 1/2" thick steel. No wimply aluminum stuff allowed in my shop.
Regards, James R. Johns>