Something nobody else has mentioned, so I'll bring it up...
Try a lighter camera with smaller pixels, something based around a mono chip such as the IMX178. Sensitive, low noise, 14-bit. If you're chasing galaxies, you'll mostly want luminance, so the small mono pixels will give you good detail/resolution but you'll have the benefit of imaging at f/4. As a result, your subs won't need to be too long.
Of course it doesn't get around the need to balance your scope carefully. I've taken shots with C11+reducer+OAG+DSLR...probably not much shy of 18kg...it's doable, but a breath of wind and it upsets the guiding
