The Wing-Sung feed certainly mates perfectly with the Pilot nib. The two seem made from the same spec. The section opening is a hair too small in diameter, I think, for this combo. I hope I like it, though, as I may be stuck with it.
You could have swapped the feed too, the Pilot one is way better than the WS at handling any ink.
Also I've noticed that sometimes you need to let the nib assembly dry completely before you can remove it again.