I wanted Halon because it does not corrode wiring and does not coat things.  It will kill you if you try to breath, so hold your breath if you need to use it.  It is a CFC (Ozone destroying) and no longer available product.

 

This fire extinguisher was in a classic British Mini and I purchased it on Facebook Marketplace (patience until you find one).  The quick release was included in the purchase and I clamped it to the aluminum to drill the holes.

 

I purchased series 5000 aluminum in 1/8" thickness  The 5000 series can be bent, but as the series goes up, it becomes quite hard and will snap and not bend unless heated.  A single 12" X 12" sheet to make the mount.  I countersunk the two screw head locations on the cross strap that is on the top of the fiberglass seat with a larger drill bit.  I used a hole saw to drill some lightening holes in it.  Simple to mount with nylock nuts.

 

 

 

 

Next, the seats will be removed and taken to the upholstery shop without the fire extinguisher mounts.