Mike my understanding is that you need to use the frame numbers as reference. If your negs are dense, look at the numbers and if they are dark and spreading out then cut your development time. If the numbers look crisp or even light then you are over-exposing.
There again regardless of them being thin or dense, if I have the details and look I want from my prints then I don't worry about the text books. It's back to personal preference and how much detail you want in your shadows / highlights.
Bet I get shot down for this advice