Hi - I was reading through the archives and found this post.
There seems to still be a number of unanswered questions about not only the cage but the fuel cell requirements and what measures one can do to increase his odds in the event of a serious mishap.
One of the things that can be done is to implement a rollover valve such as the ones made by Fuel Safe for the fuel filler line.
Here is a link to IO Port Racing Supplies where they sell the FV290-A rollover valve
IO Port Racing Supplies: Fill Valves & Caps ... This is the valve that is required by NASA for use on the Factory Five Challenge cars (which also use a Lemans filler cap along with an OEM Screw-on cap beneath).
You would also want to vent the cell(s) via rollover check valves.
One thing here that has not been said is that there should be some allowances made for the compression of the cell. Since fuel (or any liquid I'm aware of) will not compress, there needs to be some room left in the tank / cell to accomodate some degree of compression. Back in the olden days, there would be people using Ping-Pong balls in the fuel cells as they were light and apparently made of a material that was not compromised by the fuel itself. There are other ways - such as the creation of a "dead-space" within the cell or other materials that could be used. I've even seen re-sealed 1 liter plastic soda bottles used but don't recommend them..
Double-wall cells - I think a good case could be made for creating another skin from steel to essentially separate the passenger compartment from the cell itself.
I would advise anyone to seek out the local Chief-of-Tech scrutineer from their local SCCA region prior to just building it with the hope that it will pass..
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Getting classified in ITE - Pretty much everything said here is right on the money. However, one thing that I've found that holds true in most every SCCA Region is that the class ITE pretty much requires that your car has either been log-booked by another "Professional Sanctioning Body" or you have proof that your car has competed in another professional sanctioning body's event. The later is much more difficult to prove to the scrutineers than you might know. The rationale behind "Professional" is to keep you from declaring that you have competed in some unknown fly-by-night sanctioning body - the sole purpose to get you into an SCCA event..
SPO - I've built and log-booked a couple here. The real catch is that the car must be capable of passing the GTn GCR rules requirements. They are very strict. My Factory Five Challenge car was originally equiped with Carburetor and I managed to get it log-booked as a GT1 rather than SPO because I wanted to have the option of running GT1 if I desired. It was tough. The cage requirements of GT1 are very specific and they will not waiver. Bolt-In vs. Weld-In. Bolt in cages are allowed but require that you have a specific square inch value in the base. Also, many scrutineers will not pass a bolt-in unless it has a backer plate the same dimension as the base plate to "sandwich" the floor-pan of the car in between.
Gotta run and work on a couple of new cars we are building but will be giving this thread some more thought.
