All very good points about a natural arc on longer putts.
During my SeeMore lesson, the SPi instructor (Chris Carfanga - awesome!) had me make strokes up against an Eyeline incline board. He explained it this way:
1) If you look at the putting stroke from down the line - the putter head follows a straight line (it slides along the plane of the board - which is a straight line). But...
2) If you look at the stroke from overhead, it has to follow an arc - like any golf swing. So from that point of view, the putter travels in- to out, squares up at impact, and then travels inside along the same arc.
Anyway - I stopped thinking about "SBST vs arc" after that. Just worked on keeping things simple & eliminated variables in the swing. SeeMore is fantastic for that IMHO.
After re-acclimating myself this winter to the RST process, some set up adjustments, and now the confirmation of face balanced at impact, I'm done.
The SeeMore process just makes too much sense. The ball is always in the same position with RST, trust it, clear your mind and stroke it. I had a tendency to keep checking the "cover the dot" too many times and mentally that got in the way. I'm over that and now a face balanced at impact convert.
I ran into this at first, but after a while I realized that I didn't need to watch that red dot during the whole stroke. Once I had enough practice, I verified that it was in fact staying hidden for the entire stroke, and I got a lot more confident that I could make that same stroke on the course & repeat it.