I'm putting together our new to us (homebuilt) Pitts S-1S project after recovering the wings, and ran into a slight issue mounting the upper wing. Once the upper wing was aligned, we noticed that the trailing edge appeared to be much higher than any Pitts we've seen. The rear spar attach bracket is also larger than the other Pitts S-1S' on the field. No mention of any modifications in the logbooks, but this aircraft was a former Reno racer as well as IAC advanced competitor. Can anyone help shed some light on this modification? *note the middle holes do not align with the forward attach bracket. Not sure what they were used for.