KimK
Your 6 weight should be good for the Trinity and the Yuba.
I like to fish the Yuba from the Sycamore ranch east of Yuba City.
It is an rv and camp ground. For $5, you can park your vehicle at the end of the campground wade across the little creek and walk about a quarter of a mile to the River. It is river right fishing and some very big native trout/or small 3-5 pound steelhead are along the river there. There are a few wiley old Brown Trout that a 7 weight rod can't budge from their holes. You think that you have hooked the bottom, and suddenly the bottom moves and shakes its head like a pit bull dog.
Some people drive over the creek to get to the river. I got stuck two years ago and it took the owner with two caterpillers to pull my Bronco out. That is the only time my 1996 Bronco has ever been stuck. So now I walk the distance. The pain is not having any place to keep the spare rods and other equipment. If you walk, you have to carry everything in. I fish it mainly with my Sage 7136 with a floating MS 6/7, and I will be using my new Bob Meiser 5/6 two handed switch rod. In the winter time, with the heavier flows, I use my Sage 7141 with the MS 7/8 with tips and Meiser 7/8 switch rod.
The Yuba is mainly now an indicator salmon egg hatch now. The fox caddis puppa is very effective there under an indicator or classic drift with Rio's clear intermediate tip with or without the sink tip compensator. Later you will need tips and probably the nine weight in late fall/winter. There is a Skawla Stone Fly hatch in the winter time that is incredible if you catch it. It is incredible dry fly action with without a nymph under the dry fly. Your 6 weight will be perfect
There are a lot of places on the Russian that you can use either rod. There is a place south of Healdsburg where you park and walk in about a quarter of a mile and have about 1 mile or river right below the creek the hatchery fish go up. Ask your local fly shop for directions. Then later in November, you can drive to Monte Rio and park under the bridge or in the little parking lot for the steelhead run. The river is narrow there, but bring your nine weight and some good tippets. The natives are big and hot and a 6 weight will not handle them. You will need a line with interchangeable tips.
Then, when the season is in full you can pay 5$ to fish Cassini's ranch. It has miles of river left. After some heart breaking Fluorocarbon breaks, I stick with Maxima tippet material. Only use your nine weight. The hottest California steelhead I have ever hooked have been at Cassinis and up at Monte Rio. They come in from the Ocean on the last high tide and swim upstream to get away from the dam seals. The next high tide they are hot, mad and charging upstream. By the time they get further north like at Healdsburg, they are still good fighters, but they have lost the torpedo speed and bull runs they have at Cassini's and Monte Rio.
There are other areas on the Russian, where you can fish but you need a map to find legal parking places and fishing places. Your local stores have them.
Your 6 weight should be okay in the Gualala. Be ready to overhand cast it if snotty one handed fishers come up. I use my 7136 with the MS 6/7 floating line or Bob Meiser's 7/8 10'6" rod with a WC 678 with tips if other fishers are close. Bob's rods are great on over handed casts and if fly fishers aren't close, it will do a good Double Spey or Snake roll.
On all of these waters I limit my tippets to 8 or 10 pound test. If you get a salmon, you want to be able to break off quickly so you don't hurt the fish or it tears up your line, rod and reel.
