Low energy limit of ‘charge increase process’ for proton in Geant4-DNA model

Dear experts,

I am trying to simulate the passage of 1keV proton through water by Geant4-DNA model. However, I find the low energy limit of ‘Ionisation process’ and ‘Charge increase process’ for proton is 100 eV. I really want to know whether it is possible to turn down the low energy limit? If it is possible, please tell me how, even I know this may result in higher uncertainty.

Thanks in advance.