What is the common thickness for rear bumper build (swing out tire carrier and top basket)?
I have 3.5" X 3.5" Sq tubing that is 1/8" thick, running stock wheels and tires (may go a little bigger, 29" maybe)
Thinking of using 1" spindle and build off it for pivit point.

Thoughts?

I'll be watching this as well, I'm going to attempt my first bumper in a couple of weeks.

1/8 inch is what I have found for normal (tire carrier, hi lift jack or rack) if running 31 and up you will need to increase thickness.
I just built 1/8" front
Did search and found 1/8" is adequate

Talked to a local fabricator that is building bumpers/ racks/ tire carriers and he is using 1/2"...
But this is for Jeeps and trucks that are going over the Rubicon running 33" tires and up, 100+ quart ice chest fully loaded and Hi-Lift jacks.

He is also using 1" spindles for the pivit points, utilizing the race and bearings

3/16's for bumper; 1/8 for carrier, etc...

if you back into anything with 1/8, it will deform rather easily...and then you will make it from 3/16ths !

Thanks for the input, I couldnt refuse the price of the 1/8" (3.5" X 3.5") Sq tubing: FREE!
So That is what I built it out of, So if it work's for I am doing I will be happy (If not... It gives me more time in my man cave to rebuild!) 

1/8 works fine. Folks try to keep the weight down on their Zuks... It's part of what makes them go places that others have trouble.

Here are a couple of photos of the bumper I built for mine. Tire off of the tailgate.. (no more rattles) Swingaway from the door and it supports a much larger tire with ease. (currently a 33" until I can locate a 34" spare)