Mike
If you lay a regular wheel flat on a table and look at it from the side you will see that the recess that the bead drops into in order to have it fit over the outside of the rim is near the top of the wheel or the side that faces out. this is a regular wheel and the way most wheels are made. If you look at a Reverse center wheel the beard recess is now closer to the bottom or the car side of the wheel and that means the recess would have to be deeper to let the bead slip over the rim on the outside of the rim. Contrary to popular beleif the bead will never stretch without damaging the tire. it is this recess that allows the bead to go over the rim. this is why reverse center wheels are not good for DIY bead locks. We usually just put a reverse wheel in the machine upside down and mout it that way.
Hope this helps
wayne