Not sure what 'very little TW time' means, but if you are under 100 hours and zero RV-8 time, the quote that Gallagher gave you is very good!
I had several hundred hours TW, SES, with just under 2000 TT when I was searching for quotes last year for an RV-8. ALso zero RV time so I had to get a few hours dual before coverage, but I pay just under $2K for a bit less than you on hull value. Thinking of, I probably should increase it.
I generally try to insure my planes for what I percieve as replacement costs. As mentioned by another poster, that number is basically made up , within reason of what you expect the plane is worth. NEVER under insure, unless you can accept less than the full value of a plane. I know of someone that got a smking deal on a plane, crosswind,bad ground loop, and the owner had been only paying for hull value of what he paid for the plane. They paid him that value, which was roughly a little more than half the planes actual value. I insured my RV8 for roughly $20K above my purchase price because after getting the plane and 'fixing' some of its issues, that is what I would expect to get if I sell the plane.