I had some hiccups for a while too until I fund what worked reliably for me. Smaller points on a heavy arrow have given me much better results. I shoot roughly 60# bows 550-650gr arrows with very sharp serrated stone points that are about 1" wide x 1.5 - 1.75 long and only 50-80 grains. I also only take shots 12 yards and under even though I shoot well out to 20. From what I have found, a marginal shot with steel can still be a good shot, but a marginal shot with stone is usually a bad shot.. basically saying, I want a double lung\heart shot on every single deer without question, or I wont release the arrow. By taking the close shots with the setup listed above, I have gotten out both sides and had a few complete pass through's on pretty much every deer I have shot. Yes you are 100% right, shooting stone is not the same as shooting steel points. I have been trying to say that for a long time..lol You do very well hunting from what I have seen in the past and I have no doubt that you will come up with a set up that works really well for you.
you are not a knapper right? If you want, I'd gladly send you a few of the points I use. You could try those out and see if they help any. not like I make the "best" points around or anything, but mine are definitely sharp and sized for killing deer from a bow. Also check out this video about mounting the points. I am not sure how you do it, but tapering into the point like I show has helped me out a lot in penetration.
http://www.youtube.com/watch?v=m_-19LW8jq0but whatever you do, don't sweat it. If it was easy everyone would do it. finish out with steel and hit it again when you feel confident again. Send me a Pm if you want and I will tell you a story..lol