Upper arm bands are not made of foam. Generally just fabric. Occasionally I will use foam on the Pbars or wrap around pads for the little guys to get used to upper arm work.
The thing is now with men's singlets/leotards is you can get a bikini cut (like briefs) or with short leggings. Nothing like having a leo ride up your crotch and crack for lil guys.
If you compete NAIGC instead of NCAA, you can get away with a men's team shirt and shorts for most meets.
Boys in the Junior Olympic Program also wear socks on certain events. Not required and not generally done on floor and vault.