Problem Payload Manager SDK odd SetEmptyMass() behavior

[Zatnikitelman]

I'm working on a launch vehicle using Kulch's Payload Manager and I've run into a major problem. For some reason, with a payload attached, calls to SetEmptyMass() always adds exactly 20500kg to the vehicle. The specific implementation is like this:

double mass = GetEmptyMass();
mass -=4500
SetEmptyMass(mass);

This only occurs when there's a payload attached with PayloadManager. When this is called with no payloads at all, it works correctly and the empty mass drops by 4500 like it's supposed to.
This is still under the 2006 Orbiter SDK with my vessel extending the VesselwithPM<myvesselclass> Payload Manager class.
[EDIT]I guess I should have asked a direct question
Does anyone know how to solve this?
Thanks for any help,
Zatnikitelman-Matt

[EDIT] To add to this topic, I've tested adding the payload through Orbiter's built-in attachment system only and I do not experience the same problem that I do when attaching a payload via Payload Manager.