This post is more an idea than a tutorial, but it might help you anyway...
On my actual project I had to modify the Pi in order to meet my requirements. Basically the Pi was too high to fit inside my Hexapod.
To make your Pi more flat, it's actually quite simple... just remove the biggest connectors and replace them by smaller ones !
This is a companion discussion topic for the original entry at https://community.robotshop.com/tutorials/show/how-to-flatten-your-pi