Once all IYRU (ISAF's predecessor) cat classes was that simple. A, B, C and D class rules was more or less set up by ISAF I think, to try and get some structure to the wild development going on back then. Now the class decides on the rules, and if it is an ISAF recognized class, ISAF has to validate changes to the rules.

If someone is starting a C class building project.. please keep us informed!