Just to let everyones see the differences, here are two SI recordings using the same track.

The blue recording is SI using the 997 GPS. It did fair as I was able to keep going straight by referencing a land mark. When I hit the dogleg (last half of video), I could not keep it in the ditch because of the slow refresh rate.

The green recording is using my laptop GPS and the same track. Notice at the last half of the recording I was able to stay in the center of the ditch while recording the dogleg.

SI settings were the same for both recordings (except noise filter).

Recording using 997 gps

Recording using laptop gps.