81mm Adapter

I liked sbeecroft's mortar below:
https://www.thingiverse.com/thing:3490682

But decided i wanted it to mount to a real set of fins. In the files you will find a new lower section and an adapter, the adapter goes in the lower section and has a 1/4-20 thread to be retained. On the other side of the adapter is a 7/8-20 thread to screw into a set of aluminum fins.

There are 2 adapters, one has integrated support and can be cut away, the other will require support to look nice.