Hi Peter
For my 80ED, I used a 340mm Geoptik bar. This one, specifically
https://www.testar.com.au/collection...en-style-350mm
It allowed me to balance my rig easily on the EQ6-R
I used the standard rings.
For my Esprit 120, I've moved over to PrimaLuceLab for the rings and bar. The downside is that their rings really only with with their own stuff. They don't use standard hole distances, but it all works well together.
Here's the setup with pictures (losmandy style, not vixen)
base:
https://www.testar.com.au/collection...andy-bar-large
rings:
https://www.testar.com.au/collection...-support-rings
top bar:
https://www.testar.com.au/collection...ar-extra-large
guide scope mount:
https://www.testar.com.au/collection...l-clamp-medium
If you stick with a vixen style, then I'd recommend something in the same length as the Geoptik linked above.
Cheers