I have two questions about Light Multiplier/Mixing Chambers for the Omega
D2 4x5 Enlarger.

First of all, there are three types of mixing chambers available according
to negative format:  4x5, 6x6 and 35mm.  If my aim were to use all three
formats, must I have a separate mixing chamber for each, or would a larger
mixing chamber also cover the smaller formats (i.e., 4x5 covers all three
formats)?

"Common sense" tells me that the 4x5 mixing chamber would work just as well
for all three, since it provides a suitable area of illumination for all
three.  But does common sense break down in this scenario?

Second question:  The diffusing "lense" in the mixing chamber seems to be
nothing more than a square piece of white, translucent plastic.  In the old
enlarger I'm trying to restore, the plastic appears to be a bit shiny and
slightly more "clear" in the center, which leads me to believe that it
would create a "hot spot" in a 4x5 print.  If I must replace this part,
could you suggest an economical source?  Would frosted glass do better?

Thanks,
Trad