Some people glue the wheels into the inner wheel. Then drill out the center of the outer wheel to get access to the nut. This works really well, but you need to buy lots of inner wheels and you can't switch wheels between the front and back.

I take a thin strip of lexan about 1/8" wide and loop it inside the outer wheel. Then I put the outer wheel on the inner wheel with ribs and slots miss aligned. This jambs the wheels together really tightly and the lexan strip keeps the wheel at a wide setting.

The x-ray pro wheel setup won't fit up without some modification. I'm really not sure if it can be done or not.