Working on something different here, the process of MOI Matching a set of irons for Zane and the impact small weight changes can have on a well well-fitted set of irons. You can get the specification correct, but if the clubs aren't correctly balanced, impact location can still be tough to achieve.
We've been playing around with clubs balanced in motion using the MOI principle rather than the static concept of swing weight matching. It's an interesting process with incredible results. We can honestly say there is something to this. All the clubs feel the same when this is built correctly. With the same amount of force required to move each club, the feel becomes incredibly consistent from club to club.
Worth a look if you're considering jumping down the rabbit hole.