I've been gathering pics while working on a cage design myself.
Here is the directory of examples.
Many of the designs won't be legal for (amature) competetion but they get you thinking

I think I'll craft my cage out of empty paper rolls, tow the car up to the fabricator and say "do this please, how much?"

haha
Gotta check with THE book for diamater and wall thickness specs...
LINKS
http://www.honda-tech.com/zerothread?id=651229
http://forums.corner-carvers.com/sho...&threadid=7978
http://e30m3performance.com/tech_art..._symposium.htm
After staring at my shell of an s13 for a while I decided that the main hoop should mount to the front of the rear seat if possible, rather than the floor, in order to give the best clearance. I'm not sure what the rules are like and I'd like to debate and talk with a cage fabricator about how it would affect the chassis rigidity and more importantly the safety of the cage. Just looking at it...I think that's the best place to mount the main hoop. I strongly suggest the rear braces to the main hoop mount to the shock towers rather than a random point of the floor or the wheel wells...this is how most of the pics have it done and should give the best strength improvements. If at all possible, brace the front shock towers. I should have a bar going straight to the shock tower from the forward part of the cage going through the dash and another from the base of the forward bars up at an angle meeting the other bar at the same mounting plate on the shock tower.