Rob. B, OK, you are correct in that there is a 5th edition. I walked up from the studio to my library and sure enough, I found the 5th edition of all places right next to the 4th edition. The 4th edition was May 1988 and had 365 pages. The 5th edition was August 1995 at 416 pages. It was 14 years ago and my memory at 66 years old (my birthday is today, August 31) is possibly fading a bit.
As a side note, I have now been working on my latest and probably last book over the last 5 years and it is getting close to completion. It is called, “The Complete Book of Golf Club Fitting and Design, The Principles, Procedures and Playability Factors”. I was always good at coming up with the longest book title names. Looks like it will be over 700 pages with over 500 drawings and photos. Look for it next year.