The only aromatizing compounds in your current plan are/is the test. I usually run mine at 400 mgs a week so I am close to your dosage. However the primo is SUPPOSED to have an anti estrogen like effect, supposed is capped because you should read up on it to understand more. I have never used it myself but I have used DiHydroBoldenone which primo is that but with a methaltion added so it’s different in overall effect.
You should have included your general body composition stats in your posting as the more body fat you carry the more you naturally aromatize test. Not sure how or why I just have read it enough and know I was a chubbier kid and I do usually have to take a higher dosage of AI. Or at least in the earlier cycles I did. So more body fat does end up meaning higher estrogen levels.
In my earlier cycles I would play with my dosage going up to .5 mgs of arimidex EOD on just test at 400 mgs a week. At that level I was still having extra water retention from estrogen.
I have since then used aromasin however never on a just test cycle, always had provi or dhb or some sort of another AAS with an anti estrogen or anti progesterone effect in the mix.
I say all that for you to keep in mind with what I am going to say next.
I would try 12.5 every other day. Aromasin has a half life of 8-9 hours about but the way it attacks the aromatase enzyme it ends up permanently disabling it. So your body has to produce more enzyme only I dont know how long that loop takes to push out more enzyme. I don’t know long it takes for your body to realize the enzyme it released is now “dead” and thus needs to make more.
You should be able to tell if you crash your estrogen because you will dry out and be very tired. The other thing to watch out for is if your estrogen is too high. The easiest sign besides gyno is water retention and high blood pressure from the extra water. I personally get the water retention and blood pressure spike way before I feel gyno. For me since I retain water in my legs I watch the indentations from thigh high athletic socks, if I can see detail from the fabric imprinted in my skin after I work out, then I know I am retaining water from the excess estrogen on cycle.
Ultimately the only way you know if your estrogen is high is through blood work. I just included my sock impression method of monitoring as a way for you to possibly develop your own method.