My gas tank skid is 1/4" steel, and the other skids (torsion bar adjuster crossmember all the way to the front) are 5/16" steel. I can't lift the big one, but you can drop the rig from just about anything and they don't budge. Overkill ???? maybe but I have the torque to push them.
I made cardboard patterns, and cut them out with my plazma cutter. The mounts are 1/2' thick and threaded for 10 x 1.5mm hardware.
I still run the stock skid under the motor, but I'm working on that one now.

Prices...(2years ago)
A sheet (30" x 6ft) of 3/8" aluminum 6061-t6 for the skids was $247.00
5/16" steel in a sheet of 3' x 4' was $29.00 this was enough to bulid the two main skids and my winch mount with some left over for???
The protection that they provide.......priceless.
Kary