Andre,
For fall on the Trinity and Klamath I typically taper my leaders down to 1x tippet, it may sound heavy but even half pounders generally aren't leader shy.
The heavier tippet allows you to put a bit more leverage on them for a quick catch and release. If the water's really clear or low, I'll use leaders down to 2x. It's more than strong enough to handle our adults if your patient and still gets the job done.
Like Ted, it's always Maxima for me. I make my own leaders and have found no other material has the right stiffness to turn over steelhead flies (weighted & unweighted) in a breeze like Maxima.
As for winter fishing on the Smith, Mad, Eel, or Mattole, I taper the leader down to a 0x tippet. Tight lines, John:smokin: