I'd send you a couple of pictures of my Trek porteur conversion.
Built the rack myself out of thinwall(0.028") steel. Painted it
with what was on sale at the hardware store. So far it's handled
up to 40lbs of groceries very well. I use it in conjunction with
back packs of different sizes and it works well this way. I'm planning
to make a bed out of plywood and high density foam shaped to hold
two 3 gallon water containers. In general, I find it's a great way
to carry things.
this summer I will build a porteur frame from scratch since I like
this prototype so much.