Formestane in minute amounts converts to 4-hydroxytestosterone, but its the prolonged usage where it can become a problem because it acts on C4 rather than C6, the ONLY formestane product I would recommend is Formastanzol for one main reason, it contains a phytoserm which is 7,8 Benzoflavone. 7,8 BenzoFflavone is an AI and stimulates LH production through gabamergenic manipulation.
After years of studying ATD, stay away from it, that is me putting it nicely.
If you don't want to go with the forma, the ONLY other AI's I recommend are , Sustain Alpha TD, and Exemestane, NOTHING ELSE for a variety of reasons. I have always been big on hormone optimization, so I know a thing or two of what worth putting in the body, and boy do I know my AI's hehe.