Hi Jared,
Not sure if this helps, but here's what I see with the G11...
If the G11 has no model, centering works perfectly. I can consistently center on any object in the sky to < 10 pixels within 3 iterations. This is < 6" for my setup. This accuracy is nothing short of unbelievable with a 30 lb payload.
When the G11 has a model, centering inherits the error in the model. If the model is good for that object, centering is good for that object. If the model is bad, centering is bad. But with a model, I will NEVER be able to achieve < 6" pointing accuracy. The model is just not that good.
In other words, I believe the ASCOM driver and mount firmware are correctly processing your slew and sync commands. It's just that the much less precise mount model is still in the equation.
I suspect this also applies for add-on (computer resident) mount models, like that used by MaxPoint and others.
Best,
KG