Hi All, I never could understand why the Arduino's did'ent have pins underneath!! I am new to the Arduino and have a couple of Uno's. But I came from using the Picaxe, where their shield and my own 20 pin version used raised sockets with the usual long square pins, so you could plug the shield in to a board, as well as a board in to the shield. So the Uno? etc could be anywhere in the stack!! I know having long pins exposed could lead to power or data shorts and problems, but think the advantage it worth it.
It just seems to make sense, you can buy a Leonardo without headers so I might do that and add my own. I have just ordered a Pololu Zumo chassis, but if you use their shield (or any other) you can only plug the Uno in upsidedown!! It just don't seem right pluging your Uno in upsidedown!! So I will be making my own simpler shield "with HEADERS" and perhaps adapting a Uno or even a Nano on a home made shield.
At present once your Uno's on there, you can't add anything else..... to the sandwich