I've attached a link to an RPOD video of a factory tour and if you look at section 2 of how the frames are built, you can clearly see that the frames are made of heavy duty carbon steel and NOT "light weight material". The frame has to be meet DOT standards in order to support the axles, walls, roof, A/C, luggage, furniture, bedding, holding tanks, and the rest of its 3000 pounds of weight.
Heres the link. https://youtu.be/QXNYA73rCNE
I'm really not interested in the warranty because a new buyer only gets a 1 year factory warranty anyway. Also if your buying a used unit, you don't get a warranty.
The factory spare tire and rim weigh in at 40 pounds. The aluminum bumper carrier from Harbor Freight weighs 17 pounds and my Yamaha 2000i inverter generator weighs 49 pounds with 1 gallon of fuel. Total weight on the bumper would be around 106 pounds.
The steel bumper I propose to weld to the heavy duty carbon steel trailer frame weighs 38 pounds and is 7 feet long and is a 4X4 square tube where a sewer hose can fit inside because its hollow.
Thus my total weight with bumper included will be 144 pounds.
Once I modify the rear bumper, my local welding shop fabricator guy tells me, it will support around 350 pounds with no issues.