Because of the location of the rings, is it going to be that crucial that they are hardox? They are really there to provide a bit of protection for the internals and make the aluminium less likely to bend at the edges if we get flipped. (The bottom one will also help against PP3D...) The main spinner is slightly further out and should take most of the big hits.

We could maybe compromise and do one ring in hardox and the other in mild steel. Then we can start the way up that makes the hardox one take the most beating based on who we are fighting.

The aluminium plates are already machined, they are 15mm. I don't think bolting it in from the side is really an option it will most likely just rip or fracture the aluminium around the bolts. Especially after seeing what Aftershock can do.

The sections will be bent as a long bar then cut up, so we just wont use the ends. Then the tabs are bolted in place on the aluminium and the section is welded to them. Which should stop it deforming too much. The added id tension should also help make the sections flush to the aluminium.

The overlaps are either both under or both over so only a maximum of 3 would need removed, although I agree a butt join would be a lot easier.

We will do the countersinking and threading so it doesn't add any cost, we can probably change the tabs to mild steel without too much loss in strength which will make our lives easier. There is no space on either side so unfortunately using nuts is a no go.

All the welding/grinding/machining is being done by our uni workshop, so its effectively free although they are really slow. The main cost is getting the material in the right shape.