There isn't anything in the F16 rules about configuration changes.

It is in the Sailing Instructions which be individually tailored for a regatta, conditions, competitors really, which is completely separate. Usually these say that the competitor needs to sail to F16 rules.

So whatever the Race Committee wants to include, ignore, change, it is up to them to note down in the Sailing Instructions. So if they want to allow indiscriminate rig changes, then so be it, but generally you would need to apply in writing to change configuration and the Race Committee would act on this request in some form or another.

Quite common in all the regattas I have been to all over the world.