This story has developed more twists and turns. It turns out I was completely wrong that the current production model of the Coleman Polar Cub is 9200 BTU. I have been in contact with the factory tech (RV Products Inc.) who told me that the 7700 BTU unit is the only model now being produced. He went on to say that he didn't think the 7700 BTU model was anywhere near adqequate to cool a 21' trailer. I had been led to believe that all new Polar Cubs were 9200 BTU because of a data sheet link in the RV Products website, as well as reading that info on some other RV forums.
Now for the good news. The RV Products tech highly recommended their Polar Mach I Power Saver a/c. This unit has 11000 BTU, but only requires 1307 watts in maximum condition mode and 1048 watts in standard condtion. He said that the Honda 2000 will start and operate the Polar Mach. So instead of swapping out my 7700 BTU for a 9200, I'll be getting the Polar Mach I. This has the same BTU output as the Duotherm a/c that
Bigfoot installs, but requires less energy. Exactly what I need - if all the facts turn out to be true. I am already confident it will be cold enough, I just need to find out whether my Honda will definitely make it work.
Needless to say, I didn't know one thing about RV air conditioners when I lived in Alaska.
Now I am in a frenzy to resolve my cooling issues before the dreaded southern summer hits me.