The easy solution would seem to be to store the weapons flat and erect them only in pairs for launch.
Actually IRL it'd probably be a VLS bay of some sort. I've only seen them shipped in VLS cells. I was just talking with odysseus1980 about that - he was interested in using my launcher design but in the end he'd probably be better off designing a boat around the same type of cells they use on Talwar. When they refit the Rajputs and Godavaris with BrahMos I'd imagine they'd rip out the fore V-125/SA-N-8 SAM launchers and replace those with BahMos VLS cells as opposed to designing a canister launcher to directly replace the P-15 launch canisters.
This really was an exercise to illustrate a point and just for fun, to come up with the smallest hull that would still float and shoot - it'd be practical, but really just barely.