I use the Tamiya T1 emitter mount on the inside on my Taigen. I have a few as they come with the Apples. I can take a picture so you know where to glue it in. Dont use super glue if the emmiter is in the mount it will fog the bulb.

If you are buying an apple for your PZ4 then you will have one. You just need the tiny screw to hold the back of the mount on so the emitter stays in. Using this mount allows you to field replace the bulb should it fail or get weak.

Like gary said the plastic is good because you can dissassemble it and remove the hatch for Battles. I did this on my tamiya. I also have another late hatch if you are looking for one.

What does the Apple mount look like? Is it the white one for the clark boards or is it black like the tamiya?