For Joe Neustien:

Joe:  I too like O2 but dont like  the weight and cost of a built-in system.

In my L-IVP, for the over 25,000' letdown requirement, I have a dual bail-out bottle package (from an ejection seat) mounted on the front of the wing carry-thru and oriented so that either pilot can activate it.  It is plumbed to facemasks that are carried in a little pocket on each side of the front cockpit.  This system gives each pilot 10 minutes of O2.

I also carry an aluminun "E" tank for crosscounty and night flights.  The tank mounts vertically and is retained behind the copilots seat with velcro straps.  I have a military surplus A-14 diluter-demand regulator mounted on the tank with O2 routed to a quick-donning oxygen mask (with mic) from a 747.   The "package" is easy to install and simple to operate.(KISS)

Regards,  Bill Hogarty