Many astrophotographers use the Orion ST-80 as a guide scope mounted on top of their primary OTA. The ST-80 is often held by 2 ring holders. I've never liked the flimsiness of rings, especially for such a bulky and lengthy guide scope. To resolve this, I designed (from scratch) a remix of Jeremy Jackson's clamshell idea, to fit the 90mm outer OTA diameter of the Orion ST-80.
All holes were designed to fit, at a maximum, M6 bolts.
I have included the SketchUp file so you can alter this clamshell to fit your needs if you like.
Designed in SketchUp Pro 2019.