ERCOUPE 415-E with O-200 field approval, no STC

My ercoupe has been upgraded in the past with an O-200 with a field approval and not an STC. I can’t find any change with weight and balance or CG following installation of O-200 in the maintenance records. According to the current w&b, I should be able to carry a passenger (2 occupants) and load baggage compartment with max 65lbs. But when I load data into ForeFlight I am shown to be aft of CG limits for entirety of flight unless I drop baggage weight to max 25lbs. Is there a possible error with CG and w&b? Should I look into obtaining STC to make changes or have ercoupe weighed again to solve the mystery issue? Any advice would be greatly appreciated.