I have an expended E motor. I'll saw off a 1/4" and use that in the 24mm tube for the motor block. An I'll cut off a 1/2" piece to use as a spacer and start with a D12-3. I have some Kevlar strings being glued to the top of the baffle to form a 3-string anti-zipper shock cord attachment point.

Unfortunately, I already glued the green ring to the 18mm mount. I 'll work things out so I can slide in the 18mm mount...for windy days.

Thanks all