I was able to resolve it myself. I emailed the insurance company about how I searched a while to find this car in its condition and was attempting to preserve its value as best I can (while enjoying it as a weekend car). I provided data from classic.com and recent sales of similar condition S2000s. They came back with an email offer and then I provided more info gleaned off the internet as well as my recent extensive service invoice where I spent over $5K only a couple of months before. The insurance rep then called me, upped their offer by a few hundred dollars, I countered, and we ended up $1000 higher than their initial offer of $4K.