From Tom Wishon.....this is what I use for fitting/build out. I should add in fitting take into account transition time and release (early-mid-late) for shaft profile and shaft weight.
These are the mid iron club head speedsβ¦..
mid iron speed over 72 mph β 4* increments (average player)
mid iron speed 60-72 β 5* increments (some seniors and some ladies)
mid iron speed under 60mph β 6* increments (seniors and ladies)
You can make an argument to say that over 85mph you could go with 3* increments but you never do because that will leave you with a very odd set makeup. So over 72mph you stay with 4* and just live with the fact the distance gaps will increase to 15 yds or more as speed keeps going up from 85 with the mid iron.
Think about all these factors when you play golf and possibly why your distance gaps are off and you wonder why. π