AC4's are known for their edge hold; I'd guess that you're skiing them too short for your weight. I kinda liked the 177's and I'm 164 lbs. Also note that skiing trees and bumps generally calls for different ski strengths than SG turns on hardpack blue runs. (Which are questionable anyway, considering the intermediate skiers around you.)
Given your Goats, and your need for speed/grip, I'd recommend three skis: The AC40 (or next year's 50) in a 177, since this is probably the most do everything fairly well midfat made; the Stockli XXL, which will satisfy any rational speed freak and just demolish chop, but just OK in bumps; the Blizzard 84IQ whatever, which will feel like a smoother more secure version of your AC's; and the Head iM82, which will be the easiest of the bunch at low speeds in bumps and tight spaces, will prefer speed on the groomers, but will get stiffer and stiffer as you accelerate, which takes some getting used to if it's icy. Each will handle your weight at speed and all are known for their grip.