Big thanks to Diesel and Sodar!
Did the dual battery install with Borg Warner relay as described by Diesel in the Official Dual Battery Thread. And went the extra mile by following Sodar's idea to mount the battery forward of the driver footwell. It was a pain to get it in there but better than taking up accessible space under the observer seat. Thanks guys for the great ideas and guidance.
I think I get OCD style points for using a billet aluminum battery holder for the Optima Blue top and Streetwires terminations in a place where NO ONE will see them (truth be told, I had the billet and Streetwires stuff laying around).
"This one goes to eleven." 2007 ProStar 197 TT w/MCX and Powerslot.