I mix and match between all plans - EE, Green, Red and Mix2Max, restricting EE to a max of 2 days a week. However I have been sticking the the 1/3 superfree whichever plan I'm doing.
I find it works really well for me and I always get a loss doing it this way. The times I don't is because I've had one or more flexi days rather than what plan I'm on!