Hacker help: Can I stack the larger Expedit on the smaller one?

Materials: Expedit/Vika Amon

Description: I want to stack the 4x4 Expedit on top of a 4x2 with a counter sandwiched between them. They will be secured to the wall.

MY QUESTION:
Will the smaller Expedit shelves support the larger ones? I have seen many stacked, but they are always smaller on top. I haven't seen a bigger shelf on the smaller unit.

I have a carpenter who is questioning my plan and I want to know what people think. I have a mixture of household stuff and books.

Thanks!

~ Maryanne, Brooklyn, NY