Yes I think so - I have a KK bit for Norm and just bought a fulmer french link which is slightly smaller than the KK but fits fine. I guess loose rings are more likely to pinch if they are on the smaller side?
Definately by the loose ring a minimum of 1/4" bigger although I always go 1/2" to avoid the ring pinching the side of the lips, a bit guard isn't the best option as the saliva & sweating can cause iritation too.