I don't know as it has not been tried on humans yet. But people reported increased flacid length from even 5 drops oral Pansterone. The animal studies with androsterone used HED of about 0.15mg/kg daily. If it is rubbed directly on the penis even 1mg-2mg may be enough as those 0.15mg/kg daily spread over the entire body and likely only a tiny fraction reached the penis and still had an effect.
For me there is no lower flaccid lenght increase at all from either 2.5mg Pansterone per day or from 5mg Pansterone per day while applied on the scrotum after 5days. Flaccid lenght is a short as it can be, so I do have to compare anything too much. Nor there is any erection or libido gains whatsoever.