I have the beginning of some 3DGS physics examples at my 3DGS Site at the link in my signature. There is a box stacking example in LocoLogic. Sometime soon I will be adding an example for pushing the phent's with the player in more realistic manner. The examples may help, then again, maybe not. I only had 5 or 6 boxes in the example stacked not 12. But it is set up so you can change the physic's attributes of the boxes through skills in WED, so it might help you determine what settings are incorrect, if that is the case.
Loco
... I'll take a look at it asap.