Can't find the article or blog but I remember reading about Paul Wood (PING engineer) talking about how from a physics standpoint, more compact heads worked better for more skilled players. Basically a longer/wider face makes it harder for the better player to square up the face and hit the center. This bit hints at it.
Day 8. Spent ten minutes hitting 8-iron and 6-iron indoors, off a mat, into a net. Took about as many minutes. Then, I wandered out back to do Speed Sticks. I haven't read the rules of that encouragement role, but I should: my last time (before a few minutes ago) using speed sticks, or at least measuring it, was October 25.
Just want to add that it's also related to ankle dorsiflexion. So for the last month before each round I'll take the grip end of a club and press it into the top of my calf as I rehearse the backswing and early downswing. Basically I don't want that angle from the foot to the ankle to change. Puts me in a position to work through the hip joint, which means that knee won't collapse inward. Gives me a good feel and reminder before and even during the round.