As noted by @o-lampe at https://github.com/MarlinFirmware/MarlinDev/issues/114#issuecomment-136757614 the `MANUAL_FEEDRATE` for Delta Z should be the same as XY.
As noted by @o-lampe at https://github.com/MarlinFirmware/MarlinDev/issues/114#issuecomment-136757614 the `MANUAL_FEEDRATE` for Delta Z should be the same as XY.