Something does sound crooked, but it's no reason NOT to laterally balance it. And you say that your aileron trim is halfway to the right, but is the right aileron higher than the left? If so, then something IS crooked.

First, balance it laterally.

Then, remove the wing, set the ailerons straight, and hold the wing in the center with the LE facing you. Now, this is a little tricky, but you need to close one eye, and slowly roll the wing so that the Trailing Edge slowly rises above the "horizon" of the spar.

You need to glance back and forth between the left and right side of the wing and BOTH trailing edges should appear at about the same time. I am guessing that the left TE (The one on your right as it's facing you) will appear first - meaning that the left wing's TE is higher than the TE on the right wing.

Now, look at both sides of the wing from the tip and see if you can tell if the right wing is twisted with the TE down, or if the left wing is twisted with the TE up (Or a little of both)

Now (You may need an extra set of hands for this) hold the wing down flat at the center and twist it the way you want it to go (The covering will wrinkle). While you're holding the twist, heat the covering to get out the wrinkles (Top and bottom).

Do the "horizon" check again and repeat if necessary