I think I will try to chip them out with a rotary hammer plus a pneumatic chissel (mine jackhammer!) I agree that they shouldn't NEED the connectors, as it will be a plastic box with PVC conduit...my only worry is that the insulation may be damaged when I repull the wire. Do they make PVC boxes w/o the slip on hubs, where I can just punch my own KO's ?? A guy on another BB said there is a fitting that looks like a threadless PVC chase nipple that will fit in/around the pipe, anybody know what fitting he's talking about? Seems like it would reduce the internal dia of the conduit.
In any case, if it proves too tricky, it's a call to the mason!
