I'd forego the aft platform entirely and put the gun on the rear edge of the superstructure. It's going to make astern refuelling impossible and complicate mooring operations and close manoeuvring in general.
I'd also make all the hull cutouts the same size.
_________________
“Close” only counts with horseshoes, hand grenades, and tactical nuclear weapons.
That which does not kill me has made a grave tactical error
Worklist
Source Materiel is always welcome.