I came across this a few yrs ago. Bob gave it out a a mid west seminar or workshop[can't remember which]. He had discovered that if there was more then a 1.40 or more point difference between the top 2 APV horses the #2 horses was hitting the ex a fair amount of the time. Here is a screen shot to illustrate what you ate looking for.
As you can see the #6 has an APV # of 4.14 while #2 has an APV # of 209. What you do is divide the 414 by 209 giving you a difference of.1.98. The 2 is an angle horse [it won the race]. Most examples won't be be this glaring but you will get the feel for it. A word of caution - Bob also stated that you may go days without an APV horse and some days you may find 2 or 3 on a card. I can attest that this true since I've employed this angle since I discovered it. So those of you who play exs or tris may want to test this angle out. I haven't done a survey on how many times it hit the ex[if I remember Bob gave a #] Anyway I found the angle still works today. I will start a survey today and those deciding to employ it should to. Once again thank you Bob for having shared this with the Methodology group.
Tim