turn the fuel pump off at 300 feet ie the time you need that redundancy the most, because "that's what my instructor told me to do" rather than read the POH or even consider what the electric pump is there for.
Clare Prop; At the Gliding Club in Hokkaido where I fly a Robin DR400 Towplane, it is 'Company policy' to have the electric pump on at all times when launching Gliders.
Apparently it is also 'Company policy' to have a 'new' electric pump fitted at the start of every Soaring season.
I have no argument with that.