I've heard often that inhibiting DHT too low on a cycle will severly retard strength gains.
A good bro with some good experience on the board said he threw it into a cycle and never saw the increase in hardness and density he should have expected.
However, this same bro had major problems with low dose d-bol and advised me against it. I used 3 times his dose and saw none of the sides he saw.
The point here is that everyone is different. I think elevated levels of DHT can be dangerous in terms of side effect. Many have used proscar with test and had great results. If your going to run a cycle, why not see for yourself?