Kevin,
If you got the builder's log with the plane, there might be some notes in there as to the number of washer that may have been added to obtain the correct wing incidence. Some builders even put notes on the spar as to the number of washer. Can you contact the builder?
Alternatively, did you get the "hot wire templates" for cutting the wing foam, when you purchased the plane? If so, it might be possible to make an upper surface "negative" of the templates, and where you transfer the level line from the template to the "negative". You could then lay the negative on to the upper surface of the wing at the appropriate reference point (Butt line). With the airplane level (top longerons level), the level line on the "negative" should also be level. If not, then you need to add washers appropriately. Make sense??
Another check is to see how well the inboard portion of the wing, mates up to the fuel/baggage strakes.
Steve Rothert
Long-Ez N49SR