Big Love,
I have the snorkel kit on my portable 7500 Watt Generator. After the break in of my engine, I have used propane exclusively. The common wisdom is that you may see a
small loss in power compared to gasoline - certainly nothing approaching 40% has been previously reported. (I could not measure
any difference.)
To get an answer for your specific generators, goto:
US Carb ForumThis forum has likely covered your situation and if not, ask away.
People that don't burn propane tend to want to point to the fact that propane or NG will produce a reduced power out... the fact that both fuels are already in gaseous form when they enter the carb tends to offset any reduction in energy density.
Sorry I could not answer your
specific question.