Brad,
I highly suggest you use the recipe here on TVWB. It's in the "cooking" tab up top, and you'll find it under the beef section.
Only thing I did differently was leave out the parsley from the rub (didn't feel it was necessary, as it was such a small amount) and added a little more pepper all around after rubbing. And yeah, only 20-25 mins per side (at 350 of course). I also didn't really wait for the smoke wood to burn down...I put my meat on when the smoker was at about 450-475 (meat brings the temp down to 350 quickly). At my grocery store, you can get 2 types, Santa Maria (untrimmed, with lots of fat) and regular ol' tri tip, which has been trimmed of pretty much all the fat. I used the santa maria cut, and trimmed quite a bit of fat (but left 1/4" fat cap on).
I said it before, and I'll say it again: It was absolutely delicious, some of the best beef I've had.