we ended up using a paintable caulking because the silicone wasnt bonding that good. on my buddies tank it didnt for whatever reason, but mine it didnt so we went over it with caulking then zavlared over that.
we used the silicone at 1st thinking it would hold so yeah thats what was on the face, and the edges also. then we caulked over the silicone, then zavlared over that.
thanks Ive been looking at different ways to go about making a few plywoods Ive made one using fiberglass resin but the smell is so strong and it leaches into the water and although silicone has no problem sticking to it it can get expensive depending on the tank size and since this MFK you have to go big or go home so money for materials becomes an issue anyway sorry I went off on a slight rant thank you very much for your prompt response and again sweeeeeeeeeet build!!!!!!