Hi Jason,
I've only just noticed this thread, very interesting. I used to work for a firm making laser 'engravers' - actually a large (6m long x 500dia x 5 tons max) lathe-like machine for cutting away the surface of printing rollers (rubber flexo and ceramic 'anilox'). It used typically a 2kW CO2 laser, but was generally the same technology as what you are using, physicas is physics, large or small.
Is there a beam shutter in your design? I have not read all the design specs, but I haven't seen one. You really do need one and it needs to be gravity operated. In the event of a power failure the laser can continue to lase for some (short) period of time, but certainly long enough to blind you. Our machines were festooned with warning signs one of which stated 'Do Not Stare Into Beam' below which some wag had written 'With Remaining Eye'.
A 10.6um laser beam is effectively a 'heat beam' so is invisible and in the event of an accident the only thing you will notice is the faint smell of burning flesh just as the lights go out - for good! I would recommend you wear laser safe spec.'s (they are not the same as normal safety specs) while operating the machine as the beam can reflect off all sorts of surfaces and you can't see it. I'm normally fairly casual about safety, but you really don't want to push your luck with this sort of toy.
What are you intending to cut with this beastie? Metals and ceramics should be easy enough, but you may have some issues cutting plastics, not the cutting as such, but the removal of 'sticky' fumes. We had perpetual problems of glued filtration systems when ablating lacquers.
I'm interested to see how you get on with this and you're only just up the road from me too so when I need some stainless profiles I know where to come.
Cheers
Richard