Hwy. 20 Willits to Fort Bragg, Ca. ???

We travel that route at least three times a year in a 40' DP towing a Ford Edge. In the past we had a Ford F-250 towing a 36' TT. Yes, it is narrow and winding, but it is not that big a deal. There are rigs your size and larger (including logging trucks) that travel to the coast on Hwy 20 every day. I have also used Hwy 128, but prefer Hwy 20. Just take it slow and pull over to allow faster vehicles to pass and you will be fine.

We checked the Mountain Directory West and it gives about the same information as Desert Captain. It is not recommended for larger rv's. We will be at Fort Bragg in the next couple weeks before heading to Mount Lassen. In order to do that we will drive way back south on SR 1 to route 128 then cross east to get to Interstate 5. Check out the Mountain Directory, it can save you a lot of grief.

HWY 20 is much better than any of your other options.

please delete (double post)

That highway is a full fledged workout. You will be tired when you dump out on the other side...narrow, very curvy.
But, "doable," as they say.

You will not have much fun nor will anyone who gets stuck behind you. :E The road is very tight and keeping that much rig in your lane and off of what little bit of shoulder there occasionally is will be a challenge. Please keep in mind that crossing the double yellow at any time is simply NOT an option. I would recommend you find an alternate route but then when you get free advice you pretty much get what you paid for. Good luck.

As always.... Opinions and YMMV.

:C