JP, you will not get a straight answer because we various guru's and experts can't decide how much estragen is opitimal for keeping anabolic hormones elevated or if it is even necissary for great gains. There are people who claim that a primo/anavar stack is great for lbm gains without water. Neither drug is a substrait for the aromatase enzyme, so neither converts to estragen. Both are suppressive to the htpa, and will stop all production of your natural testosterone if taken at high enough dose or for a long enough time, leaving no hormone in your body for the aromatase enzyme to act on. Anavar will actually reduce estragenic activity slightly. So, if low estragen levels greatly reduce gains, this stack shouldn't work at all. So who knows.