I appreciate the feedback. Yes, this was a group of people who mostly had not held a fly rod before
The thumb on top isn't just a muscle soreness from lack of use -- I play a lot of sports and do a lot of road cycling and know the difference between muscle building/soreness and joint pain. This is an unnatural
type of pain.
I'll stick to my own style, which is working okay. I only gave this a thought because he advocated it
. Funny, is that he preceded telling everyone to keep the elbow in and thumb on top by saying "most fly casting instructors teach casting the way that THEY cast...and if you aren't built like the instructor you shouldn't cast that way"
Irony? No, I see why he'd say that. The thumb on top thing he was explaining as a means to prevent twisting the wrist on the backcast and throwing the line around a curve. I can cast finger on top and have no problem throwing the line straight (not around a curve).
I do need more practice though -- for sure!