Check with Hartford through AARP. We have our vehicle(s) and home policies combined through them, as well as a $1M umbrella liability policy, and when I called them for a quote for full comprehensive coverage on the brand new 5th wheel we were considering (now on order), they only wanted an additional $160/yr to add it.
For full-timers with no sticks&bricks home coverage, you probably have less options for combining policies, so maybe none of this applies.