The easiest way to fix up the cannon is to change the ramps to smaller ramps and close up the gaps.
IMO it would provide a more squat cannon-type design rather than a unusually tall one.
If you're going for minigun (or might eventually) then just lower the barrel portion a block or two. I'll try to get a picture of what I'm talking about sometime.
Thanks, i'll give that a shot and hopefully it'll turn out well.
I have also added in where the RIB will be deployed from the port side (left), screenshot is attached below.

For you who can see what I have planned for it, well done and you'll see that it'll be rather interesting. For you who can't tough, you'll have to wait untill the sea-trials video I plan on doing upon completion of the ship.