With the proprietary mounting-interface removed, the optical-tube had two holes left behind...
If I'm not going to strip the optical-tube of its paint, I insert set-screws into the holes, epoxying them in place, but in this case, I wanted the tube blank, with no marque upon it. So, I filled the holes by epoxying thin disks of aluminium on the inside...
...then filled the depressions left on the outside, and all with J-B Weld steel-reinforced epoxy...
The OTA was painted. After a bit of trial-and-error, this is actually the second coat of paint...
It takes well over a week before it can actually be handled and used.