I bought a couple of repro cannon covers (with domes) for the STTNG. The right side fits without issue, using either cannon (I actually have 3 of the repro cannons and they all fit on the right side).
However the left side will not fit down over the assembly. I will post a picture later, because I don't see anything wrong with the assembly but If i put the cover down over the rear of the assembly (so the rear two screw holes line up), I can not put the two "arms" in front over the front-end of the bracket (the part of the front bracket that not only captures the ball but holds the optos on the left and right side).
It is not the optos binding the cover, it is the front portion that comes to a point. (I'm guessing a picture would help here but the STTNG is currently 15 miles from me and I am sans a picture on my phone of it). The point rubs on the inside of the cover and you can't get it lower.
(I actually broke a cannon cover trying to "flex" it to fit.
I am sure these cannon covers are to "spec" as far as size as they fit the starboard cannon.
I don't there's a way to "adjust" that bracket. I looked and the only bolts are the ones holding that assembly to the lower one and the bolts holding the cannon firing coil to the plate.
Anyone have any suggestions or have a similar problem there?