...And then suddenly, I was at the airport waiting to Taxi on the runway in a small Cessna.  Wait!  That sound... the fan, it's working!  As soon as I was worried it was too loud, it had already  wound down to a bearable limit.  Apparently I do know what I'm doing.  I tested it with the switch and by turning the ignition off and everything checked out fine.

Chris tested it more by driving around and said he could barely hear it with the radio on, doors and top off, but he could hear it enough to know that it didn't run as much as he thought it would.  In fact while driving at a steady clip it wasn't needed much at all.  But in traffic or on the trail, one could definitely see it's necessity.

All in all it was a really straight forward install.  The DC controller really came through and worked better than some jerry rigged set up.  It cost all together about $110 which may be about twice as much as the homemade deal, but it wouldn't be variable would it, and it would take more work running wires here and there trying to set it up right.  Some people not only run more than one relay on their own set , but more than one solenoid in case one goes out.  So in short, the cost to component, install ease, and functionality seems plenty justifiable.