Yeah! That's awesome! I'm so glad you find it useful. I was thinking about you BBQ-ing often when I posted that, Matt, but I wasn't sure if you had rhubarb out there.
I remember the first time I put it together a lightbulb went off in my head. If you have a lot of rhubarb to use up you can definitely get away without using vinegar at all. I really dig the idea of using the components of foods to extract essential flavors. I make a hot sauce come pepper harvest that is similar by utilizing the sweetness from carrots, garlic and onions to counteract the habanero bite. It has a tremendous habanero flavor without being over the top spicy. And, if you cook often you understand that recipes are just a starting ground for using what you have.