Hmm. Two WTC. That could certainly ease the space issue.
I have been thinking about one long WTC that is 3.25" wide running most of the hull length, then having a ballast tank on each side. Just to be different.
On the WTC I would have several hatches. The design looks like:
There is a base plate with a 1/16" groove routed in it. I put a bead of silicone into this groove. Then there is the top plate. I use 1/2" aluminum C channel to clamp the two pieces together and squeeze the silicone seal.
I like the idea of the aluminum C channel - nice even pressure on the seal, and it's easy to open / close.
Here is a prototype:
When I am done there will be aluminum around all four sides.
When I was making the silicone seal I used two strips of brass to ensure I had the correct height of silicone.
It sure looks like it has a good seal.
I keep re-reading Dave and Steve's comments and thinking "if they had trouble what are the chances this is going to work..."
It's a great day for R/C sub building.