Curt (RPM) we found that in wind tunnel testing, the center caps came off at speeds over 300 MPH so we are going back to the drawing board. We were going to barce them off the chassis, but we couldn't make the wheels spin at that point.
While the suburban is pretty big, I think that you are going to need something like this for your collection of kids!
They should do a TV show about you to replace that "Jon and Kate + 8" show.