ACE's advice on edgeguarding Fox/Falco:
Any time you knock Fox or Falco offstage they should be dead. Generally you want to stay on the stage unless they up-B too close (spacies that are used to the matchup hardly ever do this). On stage, your best edgeguards are reverse uair, bair, and ftilt (usually downward angled). It is important to note that only the reverse uair will hit sweetspotters (notably frame 16 of the uair, which has massive priority at the tip of Ganon's toe and will not trade hits with firefox/firebird). Here is a picture of frame 16:
If they are coming from underneath the stage and you know the up-B will overshoot, bair is a great option for its priority and duration of its hitbox. You can also fair or even dair them as soon as they land if you know it will kill. Dair at the edge is also an option, especially if you don't have enough time to reverse uair and you're not sure if they up-B will overshoot or not - just be prepared for them to meteor cancel. Also, don't be caught off guard if/when they tech. Lots of spacies like to walltech and go straight to up-B; make sure you bair/fair them immediately. They might also try to sweetspot with a phantasm/illusion after a walltech, just reverse uair or downward angled ftilt. If they do a normal tech you're back where you started and they have more damage.
If they are even with the stage, you must be ready for a phantasm/illusion attempt. I've found that the best way to cover this is with reverse uair. Not only will it hit them if they are about to sweetspot, but if they choose to up-B instead, you will have time to punish that as well (downward angled ftilt is great here). If you don't have enough time to turn around, use downward angled ftilt (which at least forces them to sweetspot perfectly). The reverse uair may not always kill (especially on Fox), but if nothing else it should set you up for an easy edgeguard. http://www.youtube.com/watch?v=_cDR4BWEqIU#t=0m58s
Here Linguini executes the reverse uair edgeguard on a sweetspotter perfectly. A quick dropzone dair followup would have been beautiful.
If they up-B above the stage, additional variables come into play. Depending on their position they may have the option of going for the ledge (downward; diagonally for sweetspot). You should be able to recognize whether this is possible or not immediately, and be able to choose the right edgeguard. If you think they will go for the ledge, you can cover this with downward angled ftilt (because of the angle they are coming at) or a well timed reverse uair. If you think they are going to come straight at you (it's your job to teach them that this is a big mistake vs Ganon), just jab or use one of your 3 ftilts based on their height (note that it is pretty tough to jab the up-B without trading hits). This way, if they choose to go up at all and avoid you, you will have time to punish them as none of these moves have massive cooldown time (unlike a retreating fair, which is still a good option if when you think they will be coming right at you).
Btw, Linguini. I hope you don't mind me using your vid as an example, and I hope my words don't come off as a critique, as that is not the case. I know that is an old vid and both you and Chops are too good.