I just called them to see what they'd say. I said "I'm thinking about buying a boat that's 9 ft. wide".
$90 annual permit allows use of the trailer on state highways & interstates. But, if you get off a state highway or interstate, you need to contact the local city/county in charge to see about their restrictions/permits. (right, like that's going to happen every time you pull off for gas, go the mile from the freeway to the ramp, etc.)
Anything under 10 ft. in width never requires a pilot car. They didn't say anything about night restrictions.
a 24 ft. RIB with a beam of 9 ft. would be "over 8'6 but under 12 ft but not over-weight, over-height, or over-length".
The state highways that the permit covers would be on these maps:
Pilot Car Maps
Look at the second set of maps entitled: "Annual Pilot Car Maps (Legal Weight)". She explained that yellow was okay and red you needed a "Single Trip Permit" for. Those were the only colors on my maps (OC/SD) but I noticed that the bay area map had red-dotted, green, and blue too. No idea what those mean!
I think that I'll skip the permit for now. By owning a RIB, we have the luxury of playing dumb with the CHP and deflating tubes. "Sorry officer, I'll just go back and deflate the tubes."