i haven't done pbf from the ebook in a while, but i had terrific success with it. i did it three days per week at the time, and progressed on each exercise whenever i hit the target for each level. that meant being on different levels for the exercises. i suppose i'm still working on the squats level...just don't really follow the program too specifically anymore. now, i just work on the movements at whichever level challenges me.
it's a great program. keep at it.