Can the hole in the crotch of the Mister B Vac Rack be closed with a latex flap?

Covering with a latex flap on the outside alone will not work, the vacuum will suck the flap inside. But if you cover your cock and balls with a larger rubber sheet on the inside of the bed this may work better.

Never use glues or adhesives on your Mister B Vac Rack as this will void your warranty.