Felt, they'll still work you above 75, and not bypass you, if that's what you're asking.
You also can't move the RSV days, or get LC, if I remember correctly.
At least in FLL, these hybrid lines make good credit. They usually have 70-75 hours already, then get paid for trips on RSV days. There's one guy who is always over 100 credit with his hybrid line.

Tex