I have all of Jim's books, and have used 531 off and on over the past 4 years or so. I have read through 531 Forever several times now and think I have figured out something that was confusing me. Thought I'd run it past you all and see if I've got it right.
In the original 531, you would perform a rep max test, take 90%, and use it as a training max, increasing it 5/10 lbs (as appropriate) each cycle until you stalled. Then, set the TM back 3 months and repeat.
One of the things about this is that you are at something like a peak only about every 5 months or so, if I understand it right.
In 531 Forever, you set your TM at 85% of the tested or calculated 1RM, and then evaluate it periodically, either on the 5+, 3+, or 1+ days, or when you do the 7th week PR test after (for example) doing 2 leader and 1 anchor cycles. Then you calculate a new TM at 85% of this and repeat. The object seems to be to never have your TM be more than 85% of your 1RM at any point in time, whereas with the original 531 your TM would climb inexorably from 90% to 100%, at which point you would set things back 3 months.
If I understand this correctly, then you are not going up and down on a five-ish month cycle, but more or less moving forward continuously.
Do I understand this correctly?