I gather some videos where down-air might be useful in actual tourney matches but its situational.
a.) Tech chase off platform. (1:26-128).
Isai vs Husband
b.) Fake out ground attack KoreanDj vs Mew2king 1:40-144.
c.) KoreanDj vs Mew2king35 - 40. Light shield edge hog into up-air.
d.) As a fake out move to peach that would try to spot dodge or shield grab you : 58 secs , 1:12 secs.
I can't find matches where sheik punishes peach block down smash out of shield with sh down air around mid to high percent.
a.) Tech chase off platform. (1:26-128).
Isai vs Husband
b.) Fake out ground attack KoreanDj vs Mew2king 1:40-144.
c.) KoreanDj vs Mew2king35 - 40. Light shield edge hog into up-air.
d.) As a fake out move to peach that would try to spot dodge or shield grab you : 58 secs , 1:12 secs.
I can't find matches where sheik punishes peach block down smash out of shield with sh down air around mid to high percent.