Victor,
One thing I have come to terms with is that even with usage of Finasteride, DHT related sides, specifically hair loss, can only be minimized versus completely prevented, especially if you are looking to minimize the impact on strength. I usually limit the dosage of Finasteride to 0.5 mg ED. I rarely go over that dosage unless I am on a heavy Test cycle (1 g) or stacking with other problematic drugs at high dosages.
I primarily focus on keeping the prostate healthy. For hairloss purposes, I will add in a combination of topical solutions instead of increasing the dosage of Finasteride. This has been the optimal solution for me and has had no noticable impact on my strength gains, but most importantly, it has prevented any prostate hypertrophy.
The other drugs you mentioned are DHT derrivities. They do not convert to DHT via the 5AR like Testosterone does. Therefore, Finasteride is useless in that application.
For detailed information about DHT concerning strength and muscle, please visit the following link:
http://www.elitefitness.com/forum/showthread.php?t=329902&page=1
Jenetic