Was it Dr. Ashby that did all of the penetration reports and studies over in Africa years ago? My memory fails me on his name but he was a major champion of the Grizzley head and what it will do. They penetrate big time and the single bevel torque combined with their tip works extremely well on bone. I had good luck with them.
If I hunted in a bit more open terrain for trailing I likely would have used them a lot more. Trailing here often involves wading, swimming, and/or crawling through almost impenetrable briars. I opted for a bit more cutting capacity and the potential to leave a bit larger hole at exit with the 4 blade Zwickey. Someone may actually offer these now but I would like to see a Grizzley with a small pair of fixed, swept back bleeders around .75" in cutting width. The bleeders could be single bevel as well if preferred. I personally believe this would make a good head even that much better. I cannot get a single bevel head as sharp as I like without lightly hitting the back side a couple of strokes with a file. I like a head to be shaving sharp and I sharpen with a Grobet file and coarse diamond stone.
A lifetime ago I hunted quite a bit with my roommate at Clemson. He was shooting an 80# Browning compound, 2419 aluminum arrows, and 200+ grain Simmons Tree Shark broadheads with a 2" plus cutting diameter. I usually shot my 90# PSE and Zwickey 4 blades with 2317 arrows. We both believed in heavy setups. Maybe a bit to heavy but we had penetration potential for sure. Anyway, he stuck a 6 point one afternoon. The shot was textbook broadside and absolutely perfect. The arrow passed right thru. There was decent blood on the arrow and some hair right where the deer was standing. We didn't find another drop of blood for 20 yards and ended up tracking mostly by tracks. We finally found the deer around 90 yards away and I don't think we found 10 drops of blood total. The hit was just like my roommate described. Perfect. Crease in, lower crease out. My thoughts were how in the world does a 2" plus wide head not leave a blood trail better than that with that placement. Later when I got a minute I looked in his quiver. Honest truth here. My lawnmower blades in general are sharper than anything i found in his quiver. Turns out he was terrible at sharpening anything. This little incident has always reinforced the fact for me that broadheads need to be as sharp as you can get them. Preferably shaving sharp. If they are dull and you can't sharpen them, find someone who can. It makes a difference.