Correct, the paint doesn't adhere to the plugs great but well enough in my opinion. I believe that's how it was originally done anyway. You could primer them and then repaint them an off white like the original color but, it works well for me to practically weather them by scratching off the paint easily to match screen references. Then I just applied a clear coat. Called it done.
Excellent. I think you're right; that's why the screen used seems to have so much paint coming off. To be honest the whole thing looks like it was fairly rapidly thrown together. They just stuck a tube in an existing gun and glue some bits to it.
I seem to recall seeing a thread where someone had identified how to add the extra holes to the MPP that don't seem to be standard to the units from the factory but can't seem to find it.
Yes, although one of the split plugs on the backside falls off at some point.
There are two split plugs on the backside on the executor bridge scene but only one in the carbon chamber scenes.
The hallway shots also show that the disc and v8 arm are on both sides in those pictures. It seems reasonable to conclude that the item was created with symmetry of the greeblies but that parts fell off as production went on.