Yaw control fins offset thrust angle?!

[MassoudGL]

So I've been spending way too much time making an SSTO that can go to Minmus (spoiler: I haven't done it). But I noticed something interesting.

Fins placed on top of my plane structure offset the thrust, by 0.1 degree in this case. Even with fins small enough that they don't offset it in the data, you can see in the aerodynamic overlay that it lifts to the left (or right if you place them mirrored). It's driving me insane though, because 0.1 is easily enough to pull me off course on the way up. So much so that my inclination is way off if I'm not constantly pulling right.

What's really weird is that it even pulls left in space. Actually noticeably more so. And the offset appears while on runway.

But then without the tail fin, there is still a 0.1 degree offset, in space and in the atmosphere, at random different points. Though never when on the ground or at low speeds. But leftward pull is far less even still.

I'm not sure the best way to post images, but here are some screenshots:http://imgur.com/a/QqOn4

I figure some of this is just changes in atmospheric drag, it's still weird that it occurs in space