[gearhead]

I carried my spare in the storage bay for quite a while, I had to move it from the under frame carrier because it would drag getting in my driveway.
I would say be very careful how much weight you put in the carrier. The bumper is very thin and just spot welded to the frame. I would suggest you get an experienced welder to "weld out" the existing spot welds. I would also try to add some buttress braces.
You may also look at adjustable receivers that attach to the frame.
Be aware when you modify anything on the frame you may void the warranty regarding the frame.