Another consideration is the regulator. A couple years ago, I depleted
a single bottle in 8-9 hours @ 17K ft. using the D1 unit. After
installing a 2nd bottle, another pilot mentioned to check the regulator
(which also came from Mountain High). Indeed, it was putting out O2 at
27psi, not the 15psi it should. I sent the regulator to MH where they
fixed it no charge. If you have the MH regulator, you might as well
send that to them too for a check.