Finally got to spend a few nights in the new rig. All went well. Only thing bothering me is that once I close the black tank valve the water stops but there is a drip that goes on for at least 10 minutes.

The valve closes OK because the drip finally stops. It's as if the pipes are so level that it takes a really long time for every last drop to drain. I'v never experienced this before in any of the 5 rigs I've owned. I can live with it I suppose but may reconsider my draining technique and duration; or install a gate valve just prior to where the sewer hose connects. I even tried tilting the rig to the drain side a bit but it didn't seem to make much difference.

The 2 grey tanks empty OK and after shutting the valves the flow stops quickly and completely.