O2 -resources for flights up to 20 000 ft / 6000 m were sufficient, and in the case of higher altitudes there were time limits for its use.
Officially recognized standards for oxygen supplies that can provide up to 15 hours flying time at higher altitudes were not met! (Klaus Ohlmann’s single seat, 15-hour flight on S 10 was double seat equipped!)
Draeger Company states: Calculate altitude 6 to 11 Km: 1 ltr (bottle pressurized 200 bar) per hour, per person)!
To carry more oxygen bottles is nearly impossible, as there is also an engine and fuel tanks which take up space.
There has to be some invention to increase the oxygen stores in these gliders. In technical terms, a bottle should be light weight, and small in size or the fuselage has to be adapted for O2 -tanks. - This is also a concern for regular sport gliders.
Oxygen equipment/material is of military origin and often old and outdated. Technical testing cannot be done easily. This is a stringent safety concern!
As long as this equipment is the only one primarily used, trained personnel and test equipment have to be available at the site by some means to keep the life support systems in first rate condition.