Hey MadDog,
I certainly am in zero position to dispute the actual company's feeding charts, but I will say that I believe they are a bit generalized, and I seem to lock my plants up anytime I use above 50% of the recommended percentage across the board for the 3 part GH Flora series. Definitely seek info. from more than myself though, as I don't want to profess that I am a pro, just sharing what I have experienced:
I run 2.5 gal res in independent 5 gal buckets, and my ppms near the danger zone if they approach 700 to 800 ppm. I run my girls at under 500 until full flower (and of course, I start lower than that when my roots pop (200 to 300 ppm).
Good luck, and peace.