Shower pan Drain Line Leak- Help!

Have an RPod-195.  Have a leak that shows up right where the gray water tank comes through the under carriage barrier.  No leak when draining the tank.  No leak when filling and draining the bath or kitchen sinks.  Only leaks when taking a shower (and it is not all the water from the shower, just enough to be problematic and worry me, most runs into the gray tank).  Have opened the vent inside the bathroom below the shower pan and looked at the drain below the pan and above the subfloor and dry as a bone there, so think it needs to be between where it goes into the subfloor and where it connects to the gray water tank.  Question is how to best access this?  Can I cut into the undercarriage barrier, (and if so, how to best reseal it, duct tape?) or is it best to unscrew it around the perimeter (would require dropping the propane lines, removing all the foam insulation/sealant around drains, etc).  Want to do as much as I have to in terms of disassembly, but not more than necessary.