I do exactly what you're talking about.
And the answer is "Yes" and "No".
That "intimidating regulator" isn't just a regulator. The small part is a standard propane regulator like you already have connected to your tanks in your RV. So the gas at the propane grill port at the back of the trailer is already low pressure propane.
BUT - you can't just hook that port into your generator - it won't crank. You have to run the propane through that second, LARGE thing that looks like a regulator. A very nice guy at the Champion dealer's service department told me that large thing is a flow regulator. It doesn't change pressure, it just restricts the amount of gas that flows into the generator. Without it you basically flood the generator with gas and it won't start.
Rather than take apart the hoses, regulator and flow restrictor that came with the generator, I ordered another flow restrictor from Champion, along with some hoses from the local camping supply store. I still wanted to be able to run the generator off a propane tank AND run it off the grill port. So now I have 2 sets of hoses and regulators.
For the grill port, basically you want to go from the outlet on the back of the trailer to the flow restrictor, then a second hose from the restrictor to the generator. Obviously you need all the correct gas fittings and quick connects.
I bought my factory reconditioned Champion 3400 inverter generator at a great price from these folks:
then I called their 800 number to get educated and buy the flow restrictor.
Buddy Ray - Atlanta
Jayco 2016 Eagle HT 26.5RLS
Ford 2016 F150 Lariat, 3.5L V6 Ecoboost
Max Tow Pkg, 36gal tank
Reese Sidewinder and Reese Titan 16k hitch