The traditional Santa Maria style, which kind of made tri tip popular, calls for a very hot open pit fire, with lump and smoking woods. This is a good way to do it, if you like a nice char on the outside, and more pink/red rare in the middle, and medium/medium rare at the ends. However, for me, no one in my family really likes meat less than medium, perhaps a hint of medium rare right in the center, but, for the most part, about a consistent medium/medium rare throughout the entire roast, with a nice hint of smoke from a favorite smoking wood. To achieve this, I would recommend a reverse sear method, where you start the roast out indirect heat about 250-275, with some chunks of your favorite smoking woods. Cook it at that temp until you get about 5 degrees from your target temp. Then, move the meat to direct heat. This would mean taking away your indirect diffuser, if that is what you are using, and get the coals red hot, then put the meat back on and sear on both sides about 4-5 minutes a side. One advantage I have with the Vision's very large fire box is I am able to mound the coals all over to one side, creating a direct and indirect cooking zone on the grill.
I really think on a kamado the reverse sear is the only way to go with a thicker cut of meat. It is easy to crank up the heat at the end of your cook to do a sear on a kamado. However, once to get the kamado to searing temps, it's a challenge to get the temp back down to a lower temp.
DurHusker absolutely nailed a tri tip recently doing it this method. Check it out:viewtopic.php?f=10&t=1874&p=12110#p12110
I wrote this some months ago about "the Finney Method", or "Reverse Sear Method", and why I believe it's the way to go, especially for novice kamado enthusiasts, which I still consider myself....viewtopic.php?f=35&t=427&p=2207