It's strange that Piper, who made the aircraft don't seem to know about some of these things. The Piper information manual (Report
VB-830) states that the zero fuel weight limitation applies to aircraft serial numbers 32 7740001 through 32-7840202.
Last time I checked, Australia was the only place where the wing spar was considered such a problem. A "unique Australian" AD. I did check with people in the USA and no one knew about any such AD there. I flew, owned and operated these air craft for quit e few years. I never heard of any that had wing spar problems, except for the AD.