It would be interesting to know if this is literally slingshotting . seems to me that your definitions are that you are just placing your guns closer to the target to get more distance(hence a longer ship with large gap between gun placement and centre point can give better results)

I think true slingshotting should be achievable on most ships (again longer gap between gun  and centre helps) if the the actual turning force of the ship is conveyed to the fired shells.

Perhaps what i have said above is `a given` but i wasnt sure if momentum of shell has been mentioned. at any rate it would be interesting to know what people think , are the game dynamics clever enough to cater for shell momentum.