Mike,
The safety reserve is user changeable, but not to less than 300 psi. The fact that you are getting a low gas alert at 600 or so is reflective of the anticipated gas use to the surface and a factor for potential sensor error at the low end- it also depends on the breathing rate recorded in the Cobalt. The next firmware update for the Cobalt 1, in field testing now, does alter this low gas scenario so it should not go off quite as early- PM me if you would like to try this version as one of our testers- we are looking for people who will notice things like this.
We do have plans to offer versions that allow the elimination of audible alarms, but it has not been a common request (more people complained about them not being loud enough at the beginning) so it has not made it to the top of the pile.
Ron