Here's a quick mock-up for looks and scale with the sight and drum.
Also note the new off-centered postition - this is neccesary to give it a better field of fire, more room for the ammo re-load hatch, and ejected cases can easily be dumped off the side (eventhough I have to look if this could potentially interfere with the side navigation engines and rotors).
The ammo drum still needs the skin.
So I wrapped some .25mm plasticard around it, and while it cured, I worked on the ammo feed.
The ammo drum mounted.
And a quick blue-Tac shot with the ammo feed.
In the background a large two-door hatch for the ammo and a standard sized hatch for access.