Whole sirloin tip???

I would do it like a roast or tri tip. Smoke it to about 125 to 130f then reverse sear it. That will give you a nice medium rare roast. I don't think I would cook it like a brisket, not enough fat to stay moist.

Delicious intense beefiness. Super lean, as BB said. I prefer mine a little more rare, so I usually VERY low temp smoke to only 120 IT, then oil, kosher salt, pepper, and garlic paste before a quick hot sear. Then cool on wire rack on counter, chill overnight wrapped in the fridge, then slice super thin against the grain the next day for outstanding cold roast beef sandwiches. Around here, I think they cost about the same per pound as chuck roast. I'm not certain though, we get ours with our whole steer every fall.

There is a you-tube on the internet on how to cut one into roasts, it will produce three. I use them to mix with pork for making German beer brats. Last one I bought at Sam's club was around 2.50/lb. I wait until their about out of date and they reduce the price.