Is it not possible to use a different mount that uses two rings with three screws in each ring? You would have to replace the shoe with a common finder shoe.
True, you could definitely do that. There was some decent weather today and a chance to experiment with the different quirks of this finder. I started with the finder centered in its bracket, and 8mm eyepiece centered on the corner of a rock about 1 mile away. The finder OTA bracket was as close to square as I could get it.
The two screws that mount the finder bracket on the OTA bracket can cause a wide swing in left/right adjustment depending on how tight each one is. It seemed closest to left/right alignment with the target when the back screw was pretty tight and the front was just snug enough to be secure. Tightening the back screw made it swing to the left, and tightening the front the opposite. Now that I did it a few times while watching it closely, it is probably reasonably repeatable but will still be misaligned some amount when it's not left on the scope.
The vertical alignment was below the target, meaning I needed to push the back of the tube down. This was good because that put more tension on the spring holding it all in place.
If you're having trouble with this finder definitely look at the brackets and check how much you can move the adjustment by tightening or loosening the bracket screws. At least get it as close as possible by adjusting the bracket before moving the adjustments for the finder tube.
Of course this brings up the question of how in the world do you put a bracket on a finder that can make it difficult or impossible to align with the scope? I fear only Celestron knows the answer to that. I really like it when works, it is just very frustrating to set it up and have the adjustment so far off every time. I think next time will be better with some idea of why it seemed so random before.
Now to go see if the heat plumes are gone and it's time to look at something other than a rock.