Caulking New Tub Valve and Spout

[frodnew]

Just had a plumber install a new shower mixing valve and spout. He recommended caulking around both the spout and the valve. The spout advice seemed pretty obvious. But the valve has the foam seal on the backside of the cover plate. What to the pros do? Is this foam seal adequate? Could plumber's putty behind the mixing valve cover plate replace caulk on the outside?

Bruce

[plumber1]

I would loosen the cover plate and put an excessive amount of plumbers pitty under it. When you draw it up with the cover screws excess putty will come out.
Take the spout off and putty the hole that the spout nipple comes through.
Now take some Polyseamseal and wipe it around the fixtures with a wet cotton cloth.
Works for me.