Almost a certain bet that the right side (or cell) is washed in, the left side is washed out or any combination of that. You know what works for me is the good old eyeball method of checking works best.

Just prop the airplane up more or less level on a table with something under the tailwheel then stand back directly off the ends of the wings at least ten feet, squat or sit so that your eyeball is level with height of the airplane. Now just look for any obvious washout or washin first on one side then have someone rotate the airplane and with you eye in the same orientation and look a difference in the opposite side or bay.

If there is a problem this will be pretty obvious using this method. Also while some biplanes use different incidence for upper and lower wings it should not more than just a few degrees. If you make a correction always better to wash out a panel or bay rather than add wash in. In fact wash in should never be added beyond just flat with no twist.

John