Hmm.... that's odd. Lemme check it out really quick. I'll get back to you in a minute
EDIT: I just did it myself and it works fine without a T-stance on the idle animation. This is what I did in PSA I went to attacklw3 and changed the trajectory for each attack from 1E to 10E. 10E = 270 in hex What did you do?
Go look through the PSA section for the resources and info and stuff and find out which action is marth's d-tilt. Then all you have to do is change the direction for it to 270 in both cases (normal and tipped). Pretty simple once you get the hang of it.
Okay I tried it and it works but when marth stands still why does he turn into like a T position