If the TinyShield protoboard supported just a top socket connector (female), and the TinyDuino Processor board supported both top and bottom socket connectors (female/male), then it would be really easy to integrate a TinyDuino into a custom circuit board by soldering the protoboard to headers on the custom circuit board, and then stacking the TinyDuino and other tiny boards on top of it.  Right now, I guess you can achieve the same by having everything "upside down" with the TinyDuino on top.  But it is not immediately obvious, at least it wasn't to me.

-Mark