This also applies to me I guess. I want to assist with the fleet when I can so what would be advisable with regards to limpet controllers? Currently I have 1D fuel and 1D repair fitted.
I guess it comes down to how much use you'll expect to get out of them. But 3D is also a decent option, since those can run limpets in pairs, with longer operational time. For instance, on the repair limpet wiki page it says that the 3D repair limpets will restore about 3x as much hull as the 1D, in addition to being able to launch 2 at a time (though I think that means repairing two ships at once, rather than 2 limpets onto a target).
Granted, 3D controllers are about 1.5 tons heavier than 1D, but on a large ship that isn't too bad.