It just so happens that I used Flat Plate for the Top of the Crossmember. It was just big enough for the casters to fit on with non welded side reinforcements in place. So I mocked it up to be just big enough for a snug fit. Then I decided to make it a hidden weld item, and welded them inside. No biggie, just had to grind off some Caster Metal for a Snug Fit!
