As Marv said, The IV DOES have mechanical down locks on the mains. It is also possible,  even easy, to rig the main gear so the locks don't engage.  When the cylinder is retracted there is a little play between "Lock" and "Stop". I rigged my plane by adjusting the rod to rack thread so that the piston was in the middle of the lock to stop play when the airplane was sitting on the mains and the hydraulic pressure was zero, the same condition where the stop would be needed. If the rack is adjusted too short the lock will never engage.

Regards
Brent Regan