Well Matt,

Alot of this yaw is due to the " P " factor. Your prop makes a cyclone around your tail section's and no, it does not only affect your roll axis but as well as your yaw.

I don't program a upline mix in my 9C because i'm learned to huck on a 4 channel due to past money issues (im 14). You can make your own mix depending on what kind of tx you have. Also what size aircraft are we talking? Honstley, the best way to learn to fly like a pro is don't use mixes. Most pilots are dependant on these mixes as well as all the pro's. And trust me, it's not hard to learn to get your plane to track a true upline, just pratice is all I can say.

Good Luck,
Matt - Aka Sp33d