Slick, built one of these & had the plan published in a local mag.

Swap the foam inserts over to suit whatever model.

http://users.bigpond.net.au/BAC/B-36_video_page_.html

Look in the loading batteries & undercarriage check video.

Originally it had 2 x side frames & folded flat diagonally, a shelf dropped down to hold it all square.

Let me know if you want the plan & article. - John.