Hi Steveo h,
I have been using the GH nutrients (MaxiGrow and MaxiBloom) by their schedule (recirculating program) and have found that the levels are about at the maximum. I get a small amount of 'neut burn' (brown leaf tips) but the plants are doing very well. I am also using the Liquid KoolBloom, Floralicious Plus, Armor Si, and FloraNector.
If you want to 'push the envelope' on the feeding levels, just do it a little at a time and watch the plants closely. If you see any problems developing, you can drain and start over.
Good luck with your grow.