The SlowStick has an aluminum 'fuse', and the gearbox mounts right on it. This means that there is no correction for the P-factor - the torque caused by the prop. A lot of models counter this by mounting the motor angled down and right (as viewed from the cockpit), the SlowStick doesn't.

This means that the SlowStick will tend to turn up and left at higher throttle ('left' is more noticeable than the 'up'). I have mine trimmed to fly straight and level at about 75% throttle (most of the time I fly mine just over 50% throttle, and adjust when flying full throttle). I read a post a couple of months ago on another popular RC forum where someone made a motor mount out of ply to correct for the p-factor.

If the warp in the wing is almost unnoticeable unless one goes looking for it, then I don't think it's causing your problem. The dihedral in the wing will probably counter it. Depending on how much it turns left, I would say that it's probably caused by the p-factor. I suggest you go to the local flying field and ask another experienced flyer to take a look, if my trim suggestion doesn't work.

Also, landing should be done via the throttle. Line up with the runway, then start throttling back slowly. Altitude loss should be gradual until the wheels touch. Try not using the elevator. Again, an instructor at the field is recommended for the first few flights.