I have a 130mm refractor (~35lbs with imaging gear) on my G11G with a 21lb and an 11lb counterweights. That works very well like other comments but I did have to do the basics - level and balance the mount, polar align and run/adjust the PHD2 Calibration Assistant in the latest releases (2.6.13)
The only other suggestion and it is not guiding related is to get a 12" pier extension for your mount for better mount limits with those long refractors.
Good luck,
Ken
