hi. i am trying to use your physics engine to develop game like angry birds.but there are some problems.
object are Slipping on each other and if you picking up more than 3 object you will see underneath one jumping up and down. the solution is to increase ImpluseScene itration but it will waste your CPU and in some case scene will cause bad lag.so i customize your code and add some extension to it:

this solution base on stop bodies that are not move on scene.if object did'nt move to much in 10 to 100 frames the body variable (bool sleep) will be set to true and collitions detecting - Integrate forces - Integrate velocities will be ignore it.if not slept object collide it or external forces cause to object variable will set to false.

it is really short code and simple algoritme to implementation but it has amazing result in code performance.