What I do in this MU is to get fox to about 60% or higher with techchases and dairs, and then get him in the air with either yet another dair, upsmash, scoop-uair or side-b. Then i chain a few uairs to a knee or whatever move to kill offstage. Does that help?
hmm. your tactic to get him above 60% is good, but your killing part seems risky. it´s not very good to use raptor boost in neutral game. moreover, it´s hard to chain uairs against fast fallers like fox. and hitting with an usmash is also difficult.
i would instantly go for a knee when i see a possibility.
i would say in neutral game one should use retrating nairs/bairs or uairs (to catch their approach) or dash dance grab. after hitting those and your opponent is above a certain %, go for a knee.
especially after hitting with retreating nair, when fox just apporached with an aerial, you can assume that he will miss tech and knee him.
unfortunately, fox has a gun... so he can force you to approach him.. which suuuuuux so hard, because falcons approach isn´t very good, compared to fox/falco. it´s very important to approach safely and intelligent.
but i also think, that there is no real formula to kill a fox. because it´s very luck dependent. if your opponent does mistakes sometimes, you can hope to win. but if your opponents neutral is on point, you will have a hard time - even hax said, that if both do no mistakes, then the better MU will win. and against a good fox, it´s preeeetty difficult, because their neutral game easily beats yours, if they know what to do (u tilts and well placed nair/bairs).
to my mind, it´s important as a falcon player to keep in mind why we picked him up as main (because he is the coolest and manliest char and playing with him is most fun). unfortunately, his MU sux against top 3, but we have to get over it and try to do the best we can. of course, there will be loses because of dumb MUs, but that´s how it is.