3/16 to 1/4" ?? that is a whole lot.
if you can get a piece of blue or pink foam about an inch thick, and longer than the wing root rib, try putting the wing panels side by side (top of wing panels facing each other) to check the straight line on both comparing each other.

that much trim always affect something.

Like ytell said, if you can take a few pictures of fully assembled plane from rear, we should be able to tell you more about it.

Any other Pattern pilots around you?