Here's the finalized v1 pi shield. The tinyduino attaches at the top and can be easily unplugged from the shield using the cartridge-style connector.
It includes both a 3.3v and 5v regulator, as the Tinyduino needs to run from a 3.3v source in order to have the tx pin put out 3.3v. Even though it's a 3.3v board, it will accept 5v, run at 5v and if given a 5v source, will put out 5v on the Tx pin, which will cook the rx pin on the pi. This design avoids the need for a logic voltage converter.
There is lots of Kapton tape in this design, as the 3.3v regulator has a very unusual design -- the center pin is the output voltage, and so the heat sink at the top is also the output voltage. To avoid bridging this with the ground on the 7805 5v regulator, I wrapped the 3.3v heart sink with Kapton tape. The picture above shows a mica shield, but the mica eventually tore away from the pins at the bottom (hey, they're fragile) and would freely rotate around the hole cap. Exit, mica, enter Kapton.
Tinycircuits also includes a physical extension shield, which is then connected via a AWM 20624 80C 60V VW-1 32-pin FFC Flexible Flat Cable. Unfortunately, the stock Tinycircuits cable is a bit short, about 5 inches. But, it does help. (See ribbon cabler on this older design):
I will get a screen shot of the DRAG READY, etc. readout on the Pi. It's quite handy.
Question: Is anyone else still active on this thread?