[grumpy]

68stang,
Herb Adams of VSE fame, built and sold aluminum frames for the COBRA and raced several.
Might start with his method as a thought process. The FFR frame with large tube main members will not lend it's self to a very good design, since you would have to penetrate the main member each time and TIG out both sides to get the strength. Then in turn the inserted member would have to have unusal wall thickness for proper connection, not for the member loading.
The birdcage design with stressed panels will work, similar to VSE.
grumpy