I didn't follow the cutting guide, but had some fun with this one.  Same process as above but pre salted as the original needed more.  I overdid it, but ...

Fresh bread, horse radish on top, mayo and mustard on the bottom, grilled red and yellow peppers and garden walla walla sweet onions.   A bunch of sliced tri tip.  I had three of these in 24 hours.   I need to get back to low carb, but building sandwiches is always fun.   

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Looks awesome and all but the horseradish please.

Looks to me that the left side is truly cut at 90* but on the left is about 70*. Which is ok as long as you are cutting thin slices. Would not do for fat slices, like 1/2" or more as the fibers would be longer. (not so much the muscle fibers, but the connective tissue fibers in particular.)   
That is one great looking TT. 

And, ultimately the cook can cut the darn thing anyway they like it, especially if they are the primary eater of the tri-tip too.

Agreed.  It seems to me that by the time you have a small cube of roast on your fork, ready to go into your mouth, it doesn’t make any difference if the serving cut was across the grain and you cut it with the grain to eat it, or if the first cut was with the grain and you cut it across-grain to get your bite-sized piece.  It’s the same cube-shaped piece.

I started a thread on that subject on PH—it generated considerable discussion.

That cutting guide seems odd to me.   I more or less cut mine all the way like the photo shows on the left.

I think of the tri-tip like a boomerang , I start cutting at the corner where the two ends come together at a angle, and then just keep slicing parallel to that end.  Yet, I always feel that once your looking at it in person, it's pretty obvious which way the grain is really going. 

And, ultimately the cook can cut the darn thing anyway they like it, especially if they are the primary eater of the tri-tip too.

I have to agree with LosSlowJoe on this.  Using the left side guide all the way through will deliver best results for insuring tenderness.

Last night we went back to the truffle oil italian tri-tip.   I added a calabrian chile sauce (two heaping tablespoons calabrian chile, a few ancho chiles, 4 roma tomatoes, tablespoon of rosemary, teaspoon of cumin, tablespoon of minced garlic, tablespoon of kosher salt, tablespoon of smoked paprika ... or close enough anyway.  Had great flavor, too much tomato, ended up a little bit like a salsa.)

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Dk, great looking tri tip. That sauce recipe actually sounds like a slam dunk salsa recipe with rosemary being a twist.
If you have leftovers, throw that meat and sauce in a tortilla for tri tip tacos.