I also run an Optima in my Roadster, mounted behind and to the right on the seat. It passed Tech @ El Mirage a number of times, but at Bonneville last year the SCTA Inspector said I needed it in a box because it was in the drivers compartment. He said he would let it pass as long as I had it in a box by the Sept. El Mirage. Made a box out of 3/16 steel, hey, good as ballast.
One less thing to worry about, and simple enough to do.
Tom