I had previously created custom regiments for multiplayer games for British, German, Russian and US squadrons.
However, I'm having a problem creating them for Japanese squadrons. I think it has to do with the country code. I had thought that 'JA' would work for IJA and 'JN' for IJN but I've had no luck getting them to appear in game.
DE - Germany
DU - NL (Royal Netherlands Air Force)
FI - Finland
FR - France (Normandie-Nieman)
GB - RAF (Royal Air Force)
HU - Hungary
IN - IJN (Imperial Japanese Navy)
JA - IJA (Imperial Japanese Army)
Pl - Poland
NN - None (can create yourself in Windows)
RA - RAAF (Royal Australian Air Force)
RN - RN (Royal Navy)
Ro - Romania
RU - USSR (Russia)
RZ - RNZAF (Royal New Zealand Air Force)
Sk - Slovakia
UM - USMC (United States Marine Corps)
UN - USN (United States Navy)
US - USAAF (United States Army Air Force)
If you mean the little badges that show up on the cowling of say german aircraft and the like....Then it's a good thing, and they shouldn't be there.
Japanese very, very, very rarely marked ANYTHING past the cockpit. Army regiment emblems were always on the vertical stabilizer and rudder sometimes extending to the rear fuselage, the navy in the form of alpha-numeric codes on the vertical stabilizer and rudder.
As to the sim, unlike changes that happen with I believe german, british and other nations aircraft as to various markings when units change, it doesn't with Japanese....My guess is Japanese units and markings really confused the makers which is not surprising. It is a very complex, often changing over time system, even the markings changing from aircraft type to aircraft type, year to year.