I am a newbie, but I have always been able to pick up and do new things fairly quickly. I decided to whitewater kayak, and I was styling class 5 first descents within 1.5 years; I decided that I was not going to suck at golf anymore, and I broke 80 within 1.5 years (still sucks but better than the 120s I was stuck on); I decided I wanted to play guitar, and I was in a decent band making people dance in short order. I started knapping some last year, and I will tell you that this is the most difficult, mind-warping, frustrating thing with the steepest learning curve I've ever done. EVER...BY FAR! Maybe its because I'm 53 and not 23, but still...its difficult, and it is most definitely an art. I figured out in short order that I would need to find my own rock, or getting decent was going to cost me a fortune. I'm barely better than when I started, but I have found that I can make some decent and servicible blades starting with pre-shaped slabs...sometimes. That said, I have not ruined nearly enough rock to actually get good. If anyone gets good at this without ruining a small mountain of stone, then they have to be a freak of nature with a God given gift for it.
I say this, because it might not be as much the physical limitations you mention, though that will certainly make it more challenging, but it might just be that you need to ruin a ton more rock in search of what techniques will allow you to best overcome those limitations. I have also found that having different sized (the metal) indirect percussion sticks with copper and aluminum and using indirect percussion with a belt to hold the stick (the way Jack Crafty's does it in his videos) helps a ton, because you can get the "feel" of the tool against the platforms, keep it where you want it (helps as we get older and hand eye coordination fades), and get more precise hits. When a strike does not result in what you were aiming for, there seem to be less variables to assess and tweak in trying to fix what didn't go right.
As far as holding onto the piece and not dropping it and not having it move on you when you strike it, look at some of Ryan Gill's videos...he uses direct percussion a lot, but he does most of his work holding the piece against his thigh, and he can whip out a point entirely by lap-knapping. Maybe try a combo of lap-indirect-percussion knapping. Heck, I figure I'm going to try everything I can think of or see someone else doing and in evey combination of all those techniques possible until I can figure out what works best for me in various situations...but in order to find out what works best, I know I'm going to have to ruin a lot more rock...a lot more than I already have.
Good luck, and post back on here when you figure out what is working, because you will figure it out.
