I've made my own rings out of PVC, drilled and tapped as you mentioned. Having used both, dual-ring three point holders and the simple O-ring, spring loaded holder, I much prefer the latter. I even considered making a PVC version of what I have and a custom built short stalk.
One thing I do like about mounting my finder on my ADM dovetail saddle (instead of a standard, stationary findershoe) is I can slide it anywhere along the dovetail rail. I typically use my left eye at the eyepiece so the finder is close but not in my way. Those who use their right eye might be bumping into it, so I can just slide it higher up on the dovetail rail without losing alignment. So for me, it works out better than a permanent attachment location.
Lots of different ways to go about it.
I like having lots of different placement locations for Orion/Synta finder bases.
For refractors, if the visual back has room and holes for a base on both sides of the focuser, I'll attach two bases. If I can attach a base to one of the refractor rings, I'll do it.
For Newts, I can drill a couple holes in the OTA to attach a finder base. (It is a bother, though, to remove and reinstall the mirrors.) If the Newt is in rings, I can attach a finder base to one of the rings.
Locations for finder bases on Cats is usually limited. And I'm not about to open up a Cat to drill holes for a finder base. But often you can attach a second finder base in pre-drilled holes on the back rim, at the opposite side of the focuser. Even if it will be out of sight on the other side of the OTA, that's OK for laser finders.
If a mount for a telescope has a location I can attach a finder base so that the finder will move along with the telescope, I'll attach a base there. Sometimes, if the mount has a panhandle, you can mount a finder base somewhere on the panhandle, maybe where it attaches to the mount by a screw. You'll probably need a longer screw.
Of course, the unusual out-of-the-way locations for finder bases are meant for laser finders. They can be located pretty much anywhere. You just need to be able to reach your hand to them.
Just this morning I was looking around my scopes and mounts for more places to attach finder bases. I found five, including one location on a p-gram for binoculars. Looks like another order for ScopeStuff! On second thought, I think I'll order the finder bases from AliExpress. They are a lot cheaper there!
Edited by Sarkikos, 06 August 2022 - 07:01 PM.