Good sam is a Broker representing several insurance companies. There are many Brokers like GS. I have tried to avoid GS myself but probably not an issue. ( I know .. this is a GS-owned forum!)
When we full timed and needed special Full-time liability since we had no sticks and bricks. I use Miller Ins based in Or(broker) and know others that have used Overland, based in AZ I believe. they are Knowledgeable on specific RV needs, like GS.
As a weekend warrior with a "home base" that covers your personal liabilities MH insurance is more or less an expensive auto policy. normal RV insurance is already rated based on the limited use of the RV. Some in fact give a bigger discount if you will define that "lay-up" period ... like November until April suspend its road coverage. During the time you won't drive it. Also, I was once told it's wise to have auto and RV ins by the same carrier to avoid multiple deductibles and issues if the Towed and MH are damaged in an accident. Not sure but it makes sense.
I've always used a broker and had good luck as it costs nothing most of the time and many times the rates they get are cheaper than me shopping directly. Many insurers are no longer covering MH's esp the 500,000 up ones. Good luck in your search.