Thanks - I've been thinking about a replacement nozzle for the airbrush I'm using (would like the airbrush doing what I bought it for ;-) ) so that's giving me some more ideas.

Now if I can just work out why my new Optoport V3 isn't turning my steppers (can't seem to find out what pin Enable is supposed to be configured for in MACH3) I'll be able to test it.