We've tried many different designs for frames and covers. The main thing we're learning is a lot of different things will work. This "condo" model has five small gertees attached: 10' Kitchen, 12' bedroom, 14' shop, 8' water closet, 8' arctic entryway.
The center 10 foot wide cookshack has 4 exit doors. The walls are not khana, they are 3x5' frames made with old 2x4's into rectangles. The center has the recycled metal lid roof ring with stackhole and the interior roof cover I actually made for the roof.
Heat- A fan above the stack distributes the heat to the four main rooms down to 20 above, at below zero, only the kitchen and the dayroom stay warm because they have floors, groundtarps, 2 inches of foamboard insulation covered with 3/4 inch plywood covered with floorpads, canvas (off the old Girl Scout Tent) and rugs.
I'm working on an instructable of how to build a gertee with a table umbrella roof, and a stack of 28, 3 and 5 foot studs. There's more than one way to make a cheap portable gertee that stands up to 80 mph winds! In the meantime I have a lot of pictures and a basic overview of the current set-up on my blog: http://nikiraapana.blogspot.com/2012/11/five-gertee-travelers-combined.html