I have recently finished building a heavy duty pochade box and put the details of its construction and concept drawings on my website.
If they are any use to anyone please feel free to copy them..
When I say plans that might be an exaggeration as the idea was scribbled out on some table napkins, but they are clearly viewable so I hope you will forgive their haphazard layout.
This pochade cost me less than 25 euros which I feel is a great advantage in these recessionary times.
hope this is helpful...
the website is here...