Hey John,
The Heavy weight passenger cars I'm using have 4 bulbs per car. So they are power hungry. If you have the time, maybe you feel like a road trip to me in Malvern and you can bring your meter along to see whats going on? And of course - run some trains!
Email me if interested.
One thing that confuses me..
I added a second gg1 to the load, and at 16 volts, I can run 2 GG1s and the passenger cars and the ZW-L doesn't miss a beat. Its amp meter reads around 8-9 amps. I would think that that load would be too much handle but it handles it.