Wouter ... Why not in the class rules?
If you had a XXX championship and the SI's said... One race will count (because that is how the OA runs their weekend regatta)... ... Would the class be happy with this standard? ... or would they want the class standards spelled out for the host club. Heck...Classes reserve to set a wind speed min and max for events to manage the competition.(I remember a huge protest at F18 championship in Va). Why not the number of scheduled races per day. Max number allowed, Min number for championship, max number of events to count for the series.(indeed the tornado class rules do this)
As you look down a list of class champions...I would like to know that all met a certain standard to claim that title.
Seems to me you can't or shouldn't leave such a defining issue up to each OA.
In the end... the class ensures the integrity of it's traditions, history and quality by these decisions.
As always... if they are spelled out in writing... you don't have much standing to bitch later.