That's a beautiful piece of beef Sir!!
Being an East cost boy, tri- tip is nowhere as popular as out West. But....being a butcher, I've seen interest in this cut grow, and I have limited experience ( to be honest, not great experience) cooking this cut.
Now, if I read this post right, you went indirect 1st and THEN a sear? Apparently, I've been doing this backwards!!!! I'm trying it your way next time.
All in all, it certainly looks like a delicious cook, hope you and the family enjoyed it.