Yah Ive read Primo will not work with Propecia/Proscar since it already a derivative of DHT.
As far as being harsh on the hair line , just because its a derivative of DHT doesnt mean it will cause hair loss their are other things to take into consideration , like for example how well it binds to the the androgen receptor in youre scalp. Studies have shown that even testoserone before its convwerted to DHT can cause hairloss... My dermatalogist told me this I didnt know this..
I also ran across some info when I was looking into doing Fina, and found its a no no for hair...