I am better at SID than I was. Ain't no good, but better.
My SID quilt work looks better than my other styles of FMQ.
My suggestions are the same as most everyone who commented.
Summary:
-Whichever technique, slow way down until you get good(er) at it.
-Use Machinger-gloves, some kind of finger cots (pet hair removal gloves are great!) to help take some stress off your hands and fingers.
-Spread the fabric from side-to-side a bit while moving it under the needle but don't stretch your fabric out of shape.
-Don't stretch your fingers open to much, so your hands don't cramp! Spread left hand from right hand.
-I use the SID foot for my Viking and I sometimes use the walking foot to SID, depends on the quilt sandwich.
-Stitch on the side of the seam, just a thread or two away from the seam-thread . . . if you can, if not . . . don't sweat it.
The last comment is not suitable for every quilt-temperament, it may drive you to drink your way into the other ditch with Madquilter and myself!
Use a Bigger needle with a Bigger eye if you can, but make sure it is sharp.
-This will move the needle tip off of the seam-thread.
-Watch the side of the needle and not the actual tip.
-Try to brush the needle against the fold of the high-side fabric without catching the tip of the needle in the side of the folded fabric. This acts as a distance-from-seam-thread measure.
Yes, if you change hand-spread-tension, you will change distance from seam thread and your SID will look like it has wandered a tiny bit.
Told you, this idea may not be to everyone's liking, but helps me get a better SID without freaking out about precision.