If you just turn on the havok simulation in the CK (Alt-H) the items will fall and settle according to physics just like they would in the game. If you do this in the CK and wait for them to settle naturally, they usually don't bounce around at random. The main cause of this is actually that dropping them down with the 'f' key sometimes puts them just a bit too low, so it's actually slightly inside the table/shelf/floor/whatever. Then as soon as you load it in game, havok detects the collision between the two and the clutter item 'bounces' off and ends up flying across the room. You can stop this by setting the flag, but then as soon as the player touches it at all, even just bumping into it, it will go back to havok rules. Raising the item slightly above the surface and turning on havok to let it fall naturally works best for me, and if the player bumps it while walking past it will usually just wbble a little, not launch itself across the room.