If one were starting from scratch, 1/2 inch bearings, shaft and pulleys would be plenty heavy. 1/4 x 6 flat bar on front and back, maybe 5 inch wide, would be cleaner. 4 inch bolts would leave room for lock nuts. Grey primer would match better than red oxide. And a sheet metal belt guard to save the knees would be a good idea. I just had all this Saturday and did not want to drive to town.I measured belts and used 2 online belt length estimators and still made 3 trips to Autozone to get a fit.