Not an expert, but from what I can find, I have seen mention of people taking a worn chain rings and cutting of the teeth to make a chainring. Alternately, one could take an old ring and cut the tabs off of the ring and profile them as trapezoidal shaped washers for the outside to act as fillers on the shelf. Do not know why someone could not do this. Aluminum is quite soft and very easy to work with. If you decide to cut it, mix up a little dishwashing soap (Dawn) and water to act as a lubricant on the blade.