I think @twinturbo was saying that in jest. Kosmo exists primarily for two reasons that i know of:
Bigger panels make it easier to use in a performance setting, and is a bit easier to build.
Measurements should be simple. All of those conversions are really inconvenient and unnecessary. “Measurements are for crazy people and mathematicians.”
Even over here in the states, its not terrible working in metric. I could build a case to fit kosmo without much of a fuss, although truth be told, some conversion is needed, and i hear that some folks that source aluminum front panels are experiencing issues with metric requests.
20 cm tall = 7-7/8 "
the width seems to be what ever works for that particular module .
someone suggested 2.5 cm increments .
one thing I have noticed that needs defining is the height of the PCB’s
I have had some not fit in between the rails. 17.5 cm is a good max ?
It’s nice to have a standard width but depending on what you use for panels it may be unfeasible. My PCB panels are multiples of 25 mm but for one-off modules I use cut to order aluminum, and the supplier cuts to Imperial measurements with -0 +1/8" tolerances. Fortunately so far the heights have been pretty close to 20 cm.
17.5 cm [ 7-7/8" ] is the PCB max .which would give you 1.25 cm [ 1/2" ] top and bottom clearance from your mounting rails .
the width of module is in increments of 2.50 cm [ 1" ] from 2.5 cm to what ever and of course this is tweakable to fit your needs .