CAUTION: if your ground proximity warning system does not have a function to accomodate operating using QFE altimeter settings, I would NOT operate using QFE altimeter settings; use QNH and do the math (or use Jepp QNH conversion table) to determine the proper altitude to fly. If you operate using QFE altimeter settings you may receive improper ground prox. call outs while on approach, and this is not something to try to diagnose, troubleshoot, or disable while on aproach.