I have an answer. I put everything I had into a swing at one of the outings and I got my SS to 123. My SS is typically 112 which is about 90%. At that speed, I can keep my posture and balance. Also I can hit fairways at that speed as well.

I am comparing my playing swing to my "use every muscle in my body to hit this ball as far as I possibly can" swing.

I don't measure my swing speed regularly... but I find when I try to swing REALLY hard, I don't get much increase in swing speed (and can lose speed as well). My 80% is just a number that I am using to describe the "ease" of my swing. It is not a scientific 80%.

For me 100% is the bolded.

Ok, so you can hit 123 but control it at 112. Would 112 be your 100%. 123 with no idea where it's going is just a lash, would you agree?

I think you are right Kong. If you set your "as hard as I can control" as 100%, then I always swing 100%. But, you also open up the idea that I might really go after one (during a scramble, or on a very open hole). Does that mean I am swinging 110%?

123 is absolute 100% yes. 112 is controllable 100% yes. I never thought of it like that to be honest. So, I normally swing at 100% of a controlled swing with a driver. No reason to swing less than that in my mind. I have been hitting more fairways than I miss lately.

I take a pretty slow back swing and probably 80% on the downswing. I tend to slice when swinging wide open

The highest I've ever clocked my swing at is 117 MPH. The RPMs of sidespin was in the several thousands and my launch angle was like 28*. Not a swing I want to put into play. I regularly swing anywhere from 105 to 108 which is about 90% and it goes straight and far thanks. I hope it translated to the VS Proto in S well. If not, I need to invest in an X flex shaft and i-mix adapter.

As hard as I can and still think I'm going to find the ball. That's probably 90% of the scramble swing, which isn't anything to rely on. Toning it down that little bit seems to give me the best combination of solid contact and swing speed.

I tend to give it a bit more oomph with the driver than the irons.