AP saddles definitely do not help those tall with long or lanky legs. But with ppl that are built more stout APs can be helpfull. I sat better in an AP but then again I am a Mesomorph. (an over weight one but none the less built mesomorphicly) Some ppl are Ectomorphs (tall, thin also known to be rather lanky.....and no I am not using lanky as a negative term.) Endomorph are more stout and short. Ectomorphs do not sit as well in an AP designed saddle where as many Mesomorphs can. Endomorphs do better with shorter, straighter flaps and a medium deep seat to encourage lengthening of the leg. Ectomorphs make for gracefull riders where as endomorphs can make stable riders but not nessesarily "classic" riders (center of balance is closer to the horse than a ectomorph and a mesomorph) Mesomorphs fall into a wide range, I am not a pretty rider in a classic gracefull sense but I am very effective.
I guess in all of reality I am basically mesomorphic with a little bit of endomorph because I am very short waisted. I do well in decently designed AP saddles.....in jumping saddles...not so much. BUt I now ride western and cutback "flat" saddles (aka saddleseat saddles). I do better in Equitation style saddleseat saddles.
"The question is not, can they reason? nor, can they talk? but, can they suffer?" Jeremy Bentham