Kyler,

Been lurking here for a short while and thought I'd chime in.

I'm not sure of the legality of any of this since I don't know all the
different TSO's and other rules involved.

1. Have you considered getting an aluminum or carbon fiber tank for the
oxygen? We changed to them on our ambulance and had a decrease in
weight. This might help with your ability to add a pound or two of
carried weight. Don't know what it would do to your weight and
balance. Second, the filled volume is a couple of cubic feet delivered
higher than a similar size steel cylinder. Same external size with
thinner walls means more volume at the same pressure. Check with your
supplier for details. This might mean fewer refills. But you would
have to recalibrate your usage chart.

2. Is the system high pressure or low pressure to the front of the
aircraft? If high pressure up front, you could possibly back fill by
putting a T connector just before the regulator and be able to refill
from the cockpit.

Again, not an A&P or someone knowing the rules. Just using the problem
presented to exercise my mind.

MAH