Thanks guys, I appreciate the feedback.
So if I'm using, say, an ounce of Chinook and a half ounce of Columbus as my bittering hops, each of which have a cohumulone in the 30%+ range, there is a risk of getting a real bitter character approaching the edge of harsh (don't want that...), but with my present water profile, that harshness would likely not rear its ugly head. Am I understanding this correctly?
I was also thinking that I could just move those hops forward a bit from 60 to 50 minutes to reduce the risk of harshness. With an increased sulphate level (somewhere in the 50-100 ppm range), would I be able to maximize my return on the positive characteristics of those two hops without risking harsh bitterness?