I have tried it...It seems kind of hack-ish.
To add multiple game levels/areas it seems that you must embed a game file into another
not sure if I got that right but...
I'm going to give it another go if I can load custom models into it without much trouble...
I had trouble with loading models, before you can load your custom model you have to create an object and save it to a folder, then you can load your mesh into this object but I don't remember how.