I've done a few things. Spacers being the easiest and most basic. Then I got a dew shield model off of thingiverse for my C8. Took forever to print, and unfortunately failed the first time about halfway through. That was a waste of time and filament. Then I flocked the inside to cut down on reflections.
Besides that I designed and printed mounting brackets for my mini pcs and power boxes. In the pictures below you can see both the one on my refractor and then the other picture shows my C8. I like the C8's design better because it holds things closer to the tube, but at the same time it might transfer some vibration to it. On the refractor, it raises the CG of the scope some, but works good enough for me. I've thought about redesigning it, just haven't had time.
Then I've designed and printed custom lens caps for taking sky flats, the refractor's also shown below. My C8's was made to fit on the end of the dew shield. Basically the same thing except larger.


