Try the idea of shaving the top and end bars and using 1/4 inch aluminum U shaped (channel) wings on the bars. The grooves could then be supported by metal rods positioned on each side of each frame.
Already had planned on end tabs. However I want a way to be able to handle the frame from the sides without risk of slipping or dropping. I have planned on changing the the tab design slightly. I will be up in Atlanta next week. I should be able to complete the design on paper by then and then I will do the first CAD prototype. After that I will build my first one. Then I will find what I like about it and what I don't. I will go back and change the CAD and build the next one or correct the first one if they are minor.
I have a few strict ideas in my head I want to keep as a standard.
1. The box must be have the same perimeter so it will fit with other 8 frame mediums and still work.
2. It must use simple parts. You should be able to pick up and build one of these with items readily avaliable from a hardware store. If something breaks it should be easily repairable.
3. It can't cost a fortune.
4. While the design may be a bit more elaborate it must be simple to assemble.
5. While the frames may not work from a side open hive into a standard hive. I want to be able to convert standard frame to a side frame with a minimal amount of effort.
I have a few more not so strict desires that may change as it goes along.