Understand now but if you do not intend to add various extensions your first idea is a better/stronger design,also you would not need the pinch bolts and the slot that is going to weaken the assembly @ the point of most strain, making a shaft with a step to locate the bearings so they are captive on the shaft. if that makes any sense, unfortunately i am not proficient with sketchup as i could better explain with a drawing.
regards
Mike