It looks like the hot spot in the waxed screen is actually because the screen is now so transparent that you can see the lens.
I think that's accurate, but I don't know that there are varying degrees of applying this wax to the screen (i.e., varying degrees of transparency/translucency). I might try stripping the wax and applying a light coat of dewaxed shellac (I've read that has a similar effect).
If the screen has a hotspot then you put too much wax on it. The reason why older screens are dim is because the grind of the screen is rough. The wax fills in some of the ridges thereby increasing the transparency. If you use too much, you fill in all of the edges that refract the light. If you have a hotspot, you need to thin the wax so use whatever solvent you need to do so. Keep in mind you can take off the marking on the screen with some solvents. Be careful.
The other alternative is to place a fresnel over the screen or of course just replace the screen with something modern. The wax trick works though if you do it right.
I need to strip the wax off of the screen. Hot spot is too distracting, and too difficult to compose around. I may try thinning the wax, or just leave the stock screen as-is. It's way cleaner now than when I got it, anyway...
Fantastic images. Thats what I love about these cameras. Hyper detail in small package. The sensitivity on light.. like your pic of the work shop. That hot spot on the floor shows value along with darkest shadowy corner. Amazing little cameras.