BBQ rub in small volume... updated with a missing ingredient

I told my buddy Greg about my smoked turkey adventure, and loaned me his copy of Smoke & Spice. Naturally I wanted to try something from it. Their main "rub" (a mix of dry ingredients to be massaged into what you're cooking) calls for ¾cup of paprika -- yow! I modified the recipe based on what and how much we had on hand (I'm not yet willing to commit 2 cups of dry ingredients). Here's what I ended up with:

• 1 Tbsp paprika
• 1 Tbsp salt
• 1 Tbsp sugar
• 1 Tbsp black pepper [how did I forget??]
• 1 tsp chili powder
• 1 tsp garlic powder

It called for onion powder (which we don't have), cayenne (omitted in consideration for the lovely Carol), and a lot more paprika (ditto).

I massaged it into a sirloin steak, about 1.7#. There's a little left over. The plan is to smoke it over a pan of water, with charcoal and hickory chips, low heat, long time. I'll let you know how it turns out.

Results

The lovely Carol says it's "very good." Not quite 2 hours, temperature below 230°F throughout.

And, "Why is this so tender? It's grass-fed, isn't it?"