You want to use a flexible but strong adhesive. A good rubber cement is a good choice, but let the mask air out for a few days before wearing it. The rubber cement will chemically bond to the latex. Careful, it can dry fast sometimes. The foam is gonna soak up a lot of sweat, just so you know. I guess though it is a toss up. You could have done a latex, polyfoam filled mask, skinned on the inside with latex too, buuuuuuuuuuuuuuuuuuut then the sweat would just pour out the bottom. The actually suits were made of foam latex, and that really sucks up sweat. The suits usually have to be wrung out at the end of a shooting day and dried for the next. I guess I rambled there a bit.