yes, should be fine.
"craft foam" is also often used. usually an EVA foam (ethylene-vinyl acetate copolymer foam).... pretty dense, small cell. what's typically used between the pcb and the plate to take up space.
watched the video.... if that's the profile you're going for thick PBT caps will also help push it that direction, if your pcb has relief cutouts, you can tape those (keep the flex, get back the better sound) and of course, add the foam.
plate material can also effect the sound. what plate material are you using? (for what you're going for, i'd suggest FR4, or plateless if your board supports it)