@Hman- by all means try it but I have an observation. I myself don't think the goal is to remain perfectly perpendicular in the bowing motion. The goal In my opinion is to maintain good contact with the string so the sound is right. I watch a lot of pros in youtube vids and their bows wander all over the place, of course no two bow alike either. Some employ an X pattern to their bowing ie down and away from the body then close to the body for the up with the tip moving away from the body. I've seen videos of Heifetz and Perlman where their bows wander but their sound is still amazing. I'm sure Pierre has interesting insight as to why this is.

1. to train your hand and wrist movement watch the bow while bowing slowly, steadily increasing speed while maintaining the bowing you desire visually. This can train the muscle memory of the motion to your body and all you really did is pay attention and watch. The straws or that bowing guide are physical and visual cues that can help with this.

2. try to remember when your feel your bow slipping and apply increased torsion pressure from your bowing wrist (twist). Varying places in the bow, different bow speeds, desired volume, projection and tone all depend on bow pressure and its time consuming to teach yourself.

Don't you live in my general area? If so we could jam sometime for sure, I think it would be great.

Hope this helps.