I don't see a ton of tri-tip on the forums. My Grandparents lived in Santa Maria, CA when I was small and we ate tri-tip many times back then, Grandpa sliced the roast and grilled it over charcoal. Easier to find now in LA, where I live now, than it was back then. It was seen as a local, Central Coast kinda' thing way back then in the late 1960s.
I tried smoking it like my Grandpa used to, sliced the roast into 1.5" thick steaks and smoked those. They were smoky (my wife thought too smoky) and a little dry. That was only 2 hours at 225, I believe. Next time I wouldn't slice it, but leave it whole.
How did this tri-tip turn out? Maybe you'll come back and let us know.