Jim,

Been there and done that and have the Tee shirt.

Trust me, that tool will not work on 1/2" screws. A tight fitting screwdriver tip that cannot move or damage the screw head is required unless you want to get out the old torch and start heating parts.

The impact wrench is not to over power the screw, but to kiss it with just enough force to break the corrosion and whatever else it holding it.

These are slotted, FH screws and some idiot that has never worked on a coach specified them. Later coaches have phillips screws which are not much better, but are an improvement.