Just thought I'd post an "in-progress":

     I have been looking into having copies of a "breadloaf" Westfalia tent
     made - at $40 an hour shop flat rate, it's starting to look like a
     futile efort.

     I got a firm quote of $95 materials, $180 labor just to have a canvas
     bag custom made for the Westfalia roof rack (cool idea if I might say
     so myself; sized to fit, straps and buckles to coincide with the tie
     down locations, flap-covered heavy-duty zipper, etc.)

     At this rate, a tent canvas would bite the wallet at over $1000 -
     better to buy the late-model one direct from Westfalia (see one
     person's experience at www.vanagon.com).

     I'll keep checking.

     -Blaine