I got my grey tank with 2 3/8" fpt bulkheads on the bottom. I want to add a 3/4 fpt bulkhead so i can attach a 3/4 electronic ball valve to remotely empty it. I got a brass 3/4 ID bulkhead 1.25" OD mpt with two rubber washers and a nut but im trying to figure out the best way to secure it considering i have no way to access the inside of the tank to put the nut on it. Any tips?