Mammoth and extended hitch

I have an Everest and bought a 48" Reese extension. I later cut it back to 42". With the 2" receiver and ball you gain about 5 more inches. I doubt that 36" will be long enough to insure than you can make sharp turns.The length I have works great.

Put the camper on and grab tape measure.
The hitch doesn't end with the bed, but sticks farther under the bumper.
Depends on the truck that can add 8"
Than measure trailer tongue. Some trailers will be ok with ball under the camper, some will crash on turns.
Make a jig imitating the tongue with corner of the trailer and turn it around on the point where proposed hitch might go.
You have to balance between making set danger to drive and set that will crash on turns, so you don't have margin for error.

I highly doubt 36" is enough. With my 11' camper on my Chevy dually a 48" Super Truss is barely long enough. My ball is only about 6" beyond my camper bumper.

42" with my Mammoth on a Ford. Probably best to measure after mounting the camper.

We tried a 42 inch extension with our Host Yukon and it bounced too much to carry our bikes. Went with a Super hitch too tow our Jeep.

I use a 18 inch hitch with my 9 1/2. It's long enough. A lot depends on the ball mount length.

I have more of my Mammoth on the bed than a pickup and can get away with a 36" model. I went with a 42" so I had sufficient room to slide open the tray while hitched. A pickup will need a 42" or 48" SuperTruss.

Flashman, what are you intending to tow?