Summary

This uses the ATSAMA5D3-XPLD board, based on an ARM Cortex A5.
http://www.atmel.com/tools/ATSAMA5D3-XPLD.aspx

It also uses the 4.3 inch display from PDA.
http://www.digikey.com/product-detail/en/90-00002-A0/1230-1000-ND/

Instructions

Cut out the supports with a razor blade.

You'll need at display ribbon cable of at least 200mm in length. This is because the 'XPLD board doesn't simply fold back on the PDA display.

Before you touch the display ribbon connectors, let me warn you they are very fragile and are only rated for about a dozen insertions. Go slow. Be patient with them.

There is a large cut-out in the case for the side buttons of the PDA display. There is also a large cut-out in the case for the Ethernet connectors. If both of these large cutouts are on the same side, structural integrity of the case is compromised. A design with the 'XPLD board turned 180 degrees solved this problem, but requires a 200mm cable.

The two hoods are for the connectors on the back of the PDA display. Once mounted, they come very close to the back of the 'XPLD board, so it was prudent to make covers.

Mount the first rail on the side of the PDA display with the cable. The cable runs through the slit in this rail. Mount the cable on the PDA display board, carefully thread the cable through the slit in the rail, THEN secure the rail. Secure both screws of the first rail.

Install the screw which will go in the "slip hole" of the second rail, so it is not too tight to disallow the screw, but tight enough to be snug when the rail is in place. You won't be able to tighten this screw later.

Carefully fold the ribbon cable and place the board in position in the first rail. Then carefully mount the second rail while simultaneously making sure the cable stays in between the boards and aligning the 'XPLD board with its slot on the second rail. ;-) You'll know why I inserted the smiley face after you do this. :-p

What you have now simply drops into the case. There is a protuberance on each inside corner of the case. These will snap over the rails you just mounted, holding the unit in the case.

There should be enough room for one Arduino shield, depending on the shield of course.

You can remove the unit from the case by gently prying the side with the PDA display buttons.

Case for Atmel's ATSAMA5D36 development board