A 2:1 (or higher) ratio is what I have always used in the past. If the ratio was anything less, I began experiencing low E effects. That being said, I recently adjusted my current blast (replaced tren with primo, increased T, added anadrol back in), and decided to test the waters again.
I started with 700 T and 350 primo for a week, and slowly began increasing primo and decreasing T. I'm now at 560 T and 420 primo, and have been for 2 weeks, and I'm experiencing ZERO low E effects. I don't know what changed, but so far, I can handle a lower ratio of T : primo than before. I'm actually really enjoying this combo. I will stay at this dose for this week, and then I might see if I can increase the primo some more.
I don't think it's the anadrol (50 mg/day) that's making the difference, because I've ran it before at the same dose with primo and T.
I'm not well-versed in epigenetics, so I'm hesitant to make an assertion to that regard, but something has definitely changed.