Fernco wax free seal and Drake toilet

I installed 2 Drake toilets using a Fernco wax free seal instead of the wax ring. Neither toilet sits on the floor and needs to be shimmed. Is this OK?

Are you saying that the whole toilet rocks on the flange now with the waxless seal installed? If so, I think I'd prefer to use a regular wax ring instead. If it is not actually behing held up by the seal and flange, then just shimming should be fine. This would normally only occur if the flange was higher than it should be.