Thanks for the tips!! Today was a completely clear day and I tested the panel at about 1:30pm in prime sunlight.
Open circuit voltage measured = 20.9 volts (Voc rating was 21.2 volts)
Short circuit amps measured = 6.16 amps (Isc rating was 6.10 amps)
So I can clearly conclude that the panel is working just peachy. Big relief as I was not looking forward to trying to package that up and return it.
The TriMetric 2025RV indicated the battery was at 84% when I tried the charging test yesterday where it was only drawing 1.4 amps.
I think my next couple of simple tests are:
a) drain the battery down to 60% or more and give it a test then
b) try eliminating the bargman wiring and go straight off the controller to the battery
c) eliminate the umbilical and just try panel to the controller to the battery (maybe my splicing attempts aren't that great after all)
I suspect that (b) may be adding a good 20' or more of 10 or 12 gauge copper wiring as the trailer umbilical goes all the way to the distribution panel in the back of the scamp
and then separate wires are run back out to the battery (vs. splitting off the battery supply immediately once it enters the front scamp
closet). Access is really hard to see in there so I can't discern which of those it is, but this is a really simple test.