Ok, so the Nirvash was bugging me, and I decided to get to the bottom of it.
Result 1: Broadside AI only really engages at all if your broadside turrets have Conquest-type angles - +-90 facing and 120 arc. I noticed MShadowy resetting his broadside SHI frigate's turret arcs that way, so I suspected as much ... confirmed.
Result 2: Any fixed front-facing built-in will basically stop it from broadsiding at all, including DO_NOT_AIM missiles. I mentioned the latter to Alex as it seems like a bug.
Result 3: After turning the hidden into a small energy (so I could load the game without crashing AND not have a built-in) it turned into an actual broadside ship.
Then I confirmed something I suspected - a broadside ship with NC narrow shields is a pretty awful idea, it really doesn't work at all.
The AI is not entirely dumb, and whenever it feels under threat it will turn nose-on to hide behind the narrow shield; when its not hiding half the shots will go right past the sides of the shield and turn your armor into swiss cheese.
It is, to be generous, not very effective.
I suspect the only way its going to work is it has a wider than normal shield arc, or if you turn it into a missile boat.
The latter I find frankly more interesting, as the Sledge is too fragile for mid-to-late game, especially with the small launchers and siege fusor making it go in close. I would even leave its system the same instead of giving it FMR, making it a support missile cruiser rather than an assault missile cruiser. Bashed it together quickly (
link) 10 medium missiles is too strong even without FMR. Not sure what to do there though, small Adv. P. Torps are too weak and I wanted to keep it savegame-compat for quick testing.