Cage tech question, please help!

[WhiskeyTango5.0]

I'm hoping some of you guys can help me out here. Been lurking and searching for a while. I know this post is long, but please bare with me as I'm putting the cage in this weekend and need a decisive answer quickly.

 

I'm building a cage for my '91 5.0 hatchback, following NASA regs for it in case it ever makes it to a race. I've read the GCR's and every piece of tech info on cage requirements I could find (NASA and SCCA), but I haven't been able to find any specific guidance for the placement of the main hoop base plates. The GCR's for SCCA state that "Whenever possible, the rollcage hoop should start from the floor."

 

However....

 

The car has a roll bar in it now but that's coming out. I tore up the carpet to see if I could use the existing base plate, but found that the previous builder had used what looks to be 3/8" plate (@5"x7") to mount the rollbar to the floor. Not only is this too thick, but he bent the corner of one of the plates down towards the floor so that it was close enough to weld, which gave the plate the shape of a can opener, which is exactly what it would do if it were to roll. The plate would punch through the floor and make the rollbar useless if not even more dangerous.

 

My question is this: Will my cage be NASA AI/X legal if I mount the main hoop of the rollcage to the floor of the back seats (@1" from front edge of the seat) and use proper plating (0.080 minimum) for the base, or do I absolutely have to mount it to the floor (where the can opener plates currently are)?

 

Thanks for the help guys,

Ryan

[racercosmo]

With proper support, we mount the main hoops to the edge of the rear seat bulkhead with a horizontal bar at the bottom. I believe that is stronger than the floor, plus it allows more room for the seat to be moved back.

[WhiskeyTango5.0]

Thanks Cosmo,

 

How close to the vertical edge of the bulkhead do your tubes mount? The points you mentioned are the reasons I wanted to move the bar there as well, that and the previous builder burned holes all the way through the floor with his plate welding. Oh well, at least he could build an engine!