I don't think that Fina even if it is effected by 5 alpha reductase is safe or one of the safest for hair. It's as strong as DHT in its original state. Let's assume that conversion does really happen and it does get reduced to DHTrenbolone. Logically, the strength of it, as androgen will be somewhat same as Testosteron( or dbol, or Anadrol)
In doses that most guys use now (75mg/eod) I guess, it's on a safe side. But up it to 75mg/ed or higher and your hair will start falling out.