I love me some tri-tip! My local costco usually carries them, but if they sit too long in the cooler they slice them up in to strips.
Sometimes I'll give it a little slow smoke and finish it up with a reverse sear.
That looks great. I did something similar after a failed first attempt at making pizza dough from a box mix. I used a pre-made (pre-cooked) thin pizza crust. Loaded sauce/toppings and cooked for 8-10 minutes. Turned out pretty good.
Besides pulling at a certain temperature, you can also go by feel. A temp probe should slide in and out with ease, or as some say, like a knife through hot butter. Each butt may be ready at different temperatures, but it'll normally be around 195-20…
That's a good deal on the iGrill. I got mine for Christmas and have used it a handful of times without any problems, The best part I like about it is the logging and the ability to email the data as a pdf graph, or a CSV file.