I have agreed value with Sky on my current policy. BPU NA-TT agreed at £8500. I'd be better off writing it off than selling right now! I'll be fighting to keep that value too.
Like you Scott, mine is heavily modified in the looks department, and after going through it with them, they put it down as "full body kit" which included the front wings.
I declared everything on mine, and got it to £750 (paying £75 a month over 10 months).
Have you set a limited mileage? As mine is now a second car, it's limited to 4k miles a year, and I only did 1500. That dropped it quite a bit.