MikeAeronautLZ

I do not know if the internal API of KSP allows you to get too deep into the guts of how things work, but if the decouple() function is spitting out a bogus force vector, then the solution is to spoof it. Before KAS code calls decouple(), it stores the physical data of the vessel and all the forces acting on it. Then it calls decouple, and immediately resets all that physics data in the two vessels and reapplies the force vector as it itself calculates it. It's like fixing cusps in differential geometry: isolate the point and excise it cleverly. You'd want to dump that code into a spoofed function spoof_decouple() and have everyone use that instead.

I can verify these offsets.