Av8er,
The aluminium is 3/16".
The bracketed area is two more 3/16" pieces then all 3 welded together.

I had a large bag on mine (see the pic of "Me chasing a darksider" in the Darkside sub-forum) for several trips and never had a cracking issue.
Yes it was clothing and I kept it to less than 20 lbs back there or I'd feel the rear end want to do its own thing.

Happy building!
Steve

This is the rack - loaded.
The "T-Bag" is actually on the rear seat.