Another one in line for the Wee-strom kit. I already have a Pelican 1500 bolted on as a top case, and it works great. Have you considered adapting the new 1430 top-load cases that Pelican has a side cases?? They look pretty roomy, and the top load feature would be a big plus. Also, they are only about $60 each.
I was ready to buy a couple and bolt them to an SW-Motech quick release rack, but I like your design much better. I'll be waiting....