Aaaand one more from me...

https://www.youtube.com/watch?v=LHXB931PNcE

Best 123 mph with tennis ball (questionable, likely 116mph)
Best 106 mph with 160g rusty ball.

New data with a 30" Kevlar split seatbelt sling and then a 38" Kevlar sling and a 56g tennis ball.

I switched from the 30" to the 38" when I hit 61 m/s (for referencing the plot. All values are in m/s.)

This is my best so far with a tennis ball.  Stones always seem to go faster by about ~5 m/s or so.

That would be interesting. I could do slings every 4 inches and see how it holds up.  But I really think it just comes down to the slinger for the most part.  It's hard to separate the two.


Even averages session to session will vary, or depend on how warmed up (or sore, lol) I am.

If you just consider max speed they aren't too far apart. My best with a 30" sling/tennis ball is 64, but it's only 68 with a 38" sling. But I guess that's why you would have to use an average and make sure the sampling was high enough that you gett a gaussian distribution (bell curve).