Hi,
With regard to one of your initial issues of outdoor 'drift' of about 5' that sounds suspiciously like a compass calibration issue, might be worth conducting a compass calibration away from anything metallic just to verify.
With regard to one of your initial issues of outdoor 'drift' of about 5' that sounds suspiciously like a compass calibration issue, might be worth conducting a compass calibration away from anything metallic just to verify.