After a few attempts at buying a rooftop tire carrier, viewing different options in this forum, looking at a rear carrier, looking at alex gee's brilliant designs, etc. I decided to make my own.
My main goals were to fit a large off-road tire, keep it low to cut down wind resistance and noise, be able to get the tire on and off the rack and make it with materials I could weld with my 120 volt Harbor Freight wire feed welder.
It took much longer than I anticipated since there were so many welds.
There's space behind the tire for gas cans or a large bag.
An unintended but beneficial effect of welding to the crossbars was it bowed the crossbars to approximately the shape of the roof. My original design was to have it about half an inch lower, just off the roof and between the chrome roof pieces.
This is what I ended up with.
Mount bracket and mount foot.
Side bar for loading and unloading.
Space between rack and roof.
Rear top view showing proper cover.
I didn't take any photos during fabrication.
The tire is held by a 1/2 inch bolt screwed into a bracket welded to the small bars. A 1/2 inch nut is welded to the bracket so I just load the tire, center it and screw in the bolt.
The top cover is secured with the ratchet straps, below the cover are some wood blocks I can use for jacking up the vehicle.
It's very quiet compared to my other racks and I'm very happy with the end result. It sits about 6 inches lower than the basket rack I had used.
I can post additional pictures of the mounting bolt or other items if requested.