What is applying the tension? If you are compressing the drum via the bearings, you will need tapered roller bearings; ball bearings will wear quickly. The problem with this is that tensioning bearings too much really increases their rolling resistance, so you will be wasting power overcoming bearing friction, which will be dumped as heat in the bearings. Sorry to be blunt, but my gut feeling is that this design will bend and fail after an impact with another vertical spinner.

I'm guessing this design is to allow teeth to be replaced as they wear, which is a good idea. If that is what you are after, I would go for the same design as 720's aluminium drum. It is probably no harder to make and removes all the structural problems, plus that design is field-tested and proven reliable. Mouldy made the aluminium body of the drum really thick, but you can always reduce the weight with a larger bore.