Discovered another problem. The motor coupler that I purchased from CNCRouterParts.com is too wide to clear the 1/4" steel plate as I mounted it on my Y axis. The mount works just fine when the steel plate is offset from the mounting block as designed by CNCRouterParts.com. Clever me thought that it would be better to have the steel plate hold the smaller 8020 parts in alignment.
I was about to remove the portion of the steel plate that interfered but fortunately discovered that the parts from DumpsterCNC.com will fit over the plate. I purchased a motor coupler and two shaft couplers from DumpsterCNC.com.
The photo below shows an aluminum motor coupler from CNCRouterParts.com and a delrin motor coupler form DumpsterCNC.com