I'd like to see a video of you performing that technique. Maybe that would tell me why it's so different.
My assumption here is you may be using the palm-down version at the same height as the palm-up version, and that's why it's going awry. Do the elbow strike at your shoulder level, and palm-down is definitely the way to go.
Similar for those who are finding it awkward to do palm-up. (Cough
@WaterGal Cough). If you do the palm-up variant at shoulder-height, it is extremely awkward. If you do it at belly height or lower, it's more comfortable, and playing around with it, it has greater reach than the palm-down version.
I do feel the official KKW version is stronger (but that could be because I've practiced it more), and I feel it makes more use of the augmenting hand.