Where can I find more information about the six categories and how to categorize yourself?
If you look at the MPF section on this site, you get a good explanation of what the MPF for irons is. it is not a system for categorizing your game, it is a system for identifying the playability of irons. You, as a golfer, then have information that better enables you to choose models based on each designs playability. The playability identifies primarily how forgiving and stable the iron. The higher the rating, the more “playable” the iron is for all levels of golfers. To get all the information about the MPF, in depth, you should get Ralph’s book “The Maltby Playability Factor – Understanding Golf Club Dynamics” published in 2004. That was the first book. His most current book, “The Complete Book of Golf Club Fitting and Performance”, covers the MPF and many other subjects and is a great resource book. Both of these books are available at The Golfworks.