I haven't had much time to work on this guy, but managed to get in another couple of hours today trying to refine the forms and match the screen used. There's still a long way to go until I'll be happy with it and a lot of the areas are still quite unrefined - everything needs detailed, areas need smoothed out and so on.
I always find it helpful to do a direct comparison with the screen used to improve a sculpt - so here's where I am now next to similar (but not the exact same angles) original puppet heads:
You can see the areas which I need to work on right away - I've marked all the ones I can spot with arrows and lines, this will help me when I go back to the sculpt later in the week.
I want to get this one as close as I can before calling it done, hopefully this process will help with that.
If anyone spots an obvious area for correction that I've missed or failed to notice, please do shout up. Don't worry about refinements in the detail or smoothing the skin though, that stuff only happens at the end.
Al