Mepis,
Check out this doc I found
here, you may want to adjust these settings upward to a max of 255 and test while driving using a program to track how far off you are with each. Report back as I would be interested to see some empirical results.
REG_DWORD HKEY_LOCAL_MACHINE\Software\Valhalla Legends\GPSServer\QoSAccuracy = Relative fix accuracy requested. Defaults to 64. (Max of 255, higher values request a more accurate fix, but this may increase the time to acquire a fix.)