I am building a jgro, actually a slightly smaller one. I notice in the plans that on the Y axis bearing a 0.52 inch spacer is needed. The hole for the bolt is 0.433 inch from the point of the angle iron (well angle aluminum). My calculations show that if you move the center of the hole up to 0.453 inch then you can just use a standard 0.50 inch spacer. I did that and just ordered some spacers, although I was a bit surprised at how much aluminum spacers cost.