BigT Drop:
You know your long trip will be made entirely within California, and California has an official towing speed limit of 55 mph. I have seen numerous private vehicles towing trailers pulled over on I-5 and 99. The truckers seem to usually get away with 60 -65, the CHP regularly sets up enforcement actions with 5-6 patrol cars and a light plane. There are distance marker stripes along the shoulders of the roads that the aircraft observer uses to time vehicles with and radio the cruisers on the ground, so a patrol car can catch you without even pacing you.
475 miles divided by 55 mph gives 8.6 hours, without including breaks. Are you O.K. with enough power to tow over the Grapevine pass on I-5? 101 doesn't have such long extreme grades (shorter ones near Oxnard and San Luis Obispo) but is often a major slowdown in Santa Barbara, and goes through the city of San Francisco on city streets. Also, there is construction ongoing on a new Golden Gate Bridge access from the city. I would recommend I-5 to Hwy 12 near Lodi, Hwy 12 West to I-80 (Fairfield), I-80 West just a few miles to Highway 37 in Vallejo. Highway 37 West connects with 101 near Petaluma.