selecting pace lines

[Lt1]

I have a question about pl selection. I see where FTL refers to the PL manual which does state use last line except for valid reason to go back. When I joined the Methodolgy in 1990 we were told by the Doc to use the best of the last 3 at a comparable dist and surface [within 1 furlong] and not to use a line where horse was beaten by more than 7.5 lenghts. I've been doing this with good success for 23 yrs. I will agree that most times the line I use is in the top 3 last lines. So my question is when did it revert back to the last line?. Thank you.

Tim G