the "muffler tubing" is a poke at the 20 point chrome molly cage Fran put in the SLC.
The 20-point cage is unobtrusive and available to any and all customers who want it delivered as such. Besides the door bars, which are removable, you wouldn't even know it was there. Afaik, the race roll cage was developed in Howards car, I have it in mine where it was slightly refined, and there are are others who have it too that are further refined, in particular the door bars (which I now want

). Howards, mine and the other cars were delivered with the cage installed.
Does FFR remove the center tunnel and make the other numerous obtrusive modifications to the "cage" in the GTM to make it compliant with multiple sanctioning bodies? Hardly.
I've read above where Crash refers to the SL-C in the 25 hrs. as the SL-CR, attempting to designate it as a race specific car much like your GTM-R. Not the case at all with the SL-C. The car at the 25 hour race will be what any customer can and has bought (such as myself and others) to make street legal track (and safety compliant) terrorists. That is a MAJOR distinction between the SL-C and your GTM-R.
Please don't take any of that the wrong way Richard, I've been a fan of your car since you began the build and your first 25 hour race and since then. I and I'm sure everyone else here appreciates what you have done with the given platform, no matter how much you try to downplay it
From the Superlite site for reference:
Race Roll cage Upgrade. Adds increased stiffness, and meets FIA, NASA and SCCA regulations for race car safety in most of their series- consult RCR for details before you select this option. Includes side bars that dramatically stiffen the door openings, tie-in bars to the front suspension area, additional cross bracing inside the monocoque in the front to add stiffness in the front, and other miscellaneous changes to the cage. Bolts in, and requires no welding, so it is easy to remove if you decide to convert to the street, or upgrades are added later. Interferes with the optional lower door panels (which are not needed in a race car). $3,995