I don't know if this has been found by anyone or if it's as confirmed as I think it is, but I was messing around with marth in training mode and practicing my L-canceling and I found that the soft hit of nair into d tilt will not knock down a fox up to over 200% and it can lead into a grab. I haven't tested it out of falco or any other character and I'm sure it's not very useful in actual matches, but It's very interesting and when I tested it out with a friend he couldn't jump out of it.