Ditch the extension and buy a peice of 2" square tubing lone enough for the clearance needed to replace the original that is to short. Drill the holes needed and weld a 5/8" nut on the inside to bult it to the reciever.
What was the cost of the propane generator?
Second dealer said you are much better running you generator on your diesel as it runs quieter, and save your propane for the other appliances that need propane. Cost of diesel option was about $4500
Don't let all the negative coments stop you from going down hwy1.
It is not that bad of drive with short motorhome and no toad.
You will not regreat it after seeing the view along the way.
Take your time and stop at the many senic pullouts along the way.