MIGX: setting core_path and assets_url properties

I have a modx 2.2.9 install with multiple contexts. Currently, for each context, I am overriding the system setting for assets_url so that asset paths are built pointing to a subdirectory in assets.

MIGX pulls the setting when it renders in a resource. The issue is that it can't find its connector, typically in assets/components/migx/ because the context setting for assets_url is pointing elsewhere.

What is going to be the best way to set this property for MIGX so that it points to the base level of /assets/? Adding a default property to the plugin? If I create a property set for MIGX, where is the call to attached the set to going to be at in the code?

Thanks