The next thing I've done to my spare tire carrier is to insert a solid bar of steel inside the 1" square tube to beef it up. The center needs to be stiffer so you can torque down on the hold down lugs and squeeze the tire onto the cross tube. Without the renforcement the tube will flex towards the center of the rim from the torque.
The holes that allow bolts to run towards the car have been beefed up with some crush sleaves. Just cut a small length of pipe to fit inside the square tube.
I also decided to weld the lug bolts in place so you don't need two wrenches to remove the spare now. I only tacked them on the bottom so you will only see the welds if you crawl under the car.
Next step will be to weld some 1.5" ball bearings on the ends of the tube as a finishing touch.