PhysX: stacked bricks and sleeping.

I have a construction of stacked bricks (a wall). So every brick is a rigid body. When the bricks are aligned it seems like PhysX can't put them into sleep. So I have a big performance degradation, should I place a number of these walls. But everything works fine when the wall is a little bit "damaged", so the bricks aren't aligned.

When I manually call Sleep on each brick at the start - everything seems to work fine. But when I call AddExplosionForce, the unaffected bricks are still awaken and can't get to sleep no more.

So is this a feature, or am I doing something wrong? A good explanation would be appreciated.

You may want to raise the Sleep and Sleep Angular Velocity in the project physics settings to get the desired effect that you want, these will make the bricks that are aligned fall 'asleep' easier.