That's strange - "Start Asleep" sets the same flags that cause the firemarbles in the Neighborhood to float in the air until someone bumps into them. That being said, it shouldn't be a performance penalty to leave this off. Most physics engines will automatically put dynamic bodies to sleep when they find that there is no net force acting on the body. Amusingly, in PhysX 4.1, telling a kickable to start asleep does nothing and causes them to start falling anyway. And I'm responsible for the PhysX 4.1 integration
. It's tempting to just remove the option altogether.
I do most of my testing on MOUL/PhysX 4.1, so there will probably be corner cases around the old PotS/Havok engine. It's difficult to paper over all of the changed behaviors -- some of which are accidental, unknown, and/or on purpose. Please keep reporting any problems you run into, and I'll look at fixing them in my next Korman hacking session. I did at least fix the issue where kickables would just fall through the floor when you hit them