Dave,
I haven't had any trouble with the bearing surface at all. I figured that since I had almost no money in the caulking gun tube bearing (slit to fit the diameter), I could easily replace them. However, I'm still on the first set. The wheel rims bolt through the holes that you see in the wood flange. I needed to add that flange, since the bolt pattern for the wheels was larger than the aluminum hub I built, plus, it kept everything centered up nicely.
Jack