Checked the RV a few places and the Jeep as well... center of receiver on RV was 15" center of the pins for the tow bar was 20.5" ... made a six inch riser optimum. Made a trip with the RV up to my local hitch guru, and I even discussed moving the factory hitch back an inch or 2...then we grabbed a Roadmaster 6" hi/low (model 076)
Missed by about 3/16" being long enough. So, he simply marked it and ground a radius on the backside of the extension receiver. Was able to stay out of the weld and gusset, so structurally it should be a non-event. You can compare the stock photo above to the photo below and see that he took about 1/4" of material off the back side.
It looks close to the end cap, but if the Jeep bangs the bar hard enough to get into the fiberglass I have bigger problems than the fiberglass.
The second picture isn't as good, but there's no contact with the end cap on either side:
I did talk to Roadmaster and they don't recommend using the extension and a hi/low. I don't have any reason to question the integrity of Cajun Camper's setup, I just know Roadmaster isn't willing to say "yeah, do that."
This will be a good rigid setup. Hopefully all this will be of help to someone else.