We have the Good Sam insurance previously through GMAC but now National General. Haven't had a claim but rates are good. They also allow a "storage" reduction for when your rv isn't being used. It reduces the overall coverage to just "comprehensive", and a substantial refund.
I don't know about MO, but in CA, if the rv is title free (no loan), you can actually put the vehicle in a non operation condition (through DMV) and eliminate the insurance all together. However, some insurance companies will increase your premium when you re-register. I do this with my cars that I don't use during the summer, and so far Good Sam has not increased my premiums at all.
Another good thing about getting insurance through Good Sam is that if you have any kind of a problem/dispute, you can come back here to rv.net and post your problem on the Good Sam Insurance forum and get an almost immediate response. That's a great feature....and you know what I'm talking about if you've ever tried to contact your insurance company over the phone.
Hope this helps
Ron