I've made an exercise core--and loaded it with a single pin stack that has a mushroom driver.
The cylinder is a Corbin with a CO7 keyway--which gives good room to maneuver the pick.
The problem is that the cylinder doesn't "rock back" when the pin is pressed upward. Even with absolutely NO turning tension on the cylinder, the pick's upward movement doesn't rotate the cylinder in the opposite direction--thus allowing the pin to be firmly set. It remains stuck at the "false set". It feels just like a regular set pin.
The problem is that with this condition, you can't even tell it's a mushroom driver--and since you have no indication that it's a mushroom, you're forced to manually return the cylinder to the upright condition, re-set the pin (or worse, all the pins if it were a full cylinder) and try again--only to have the same problem re-occur.
Am I just hosed on this particular cylinder type?