You definitely want an adjustable scale. In fact, I think that is the only type that is generally available. After all, you hopefully will be fortunate enough to leave DFW someday. In addition, declination is not a constant. It changes continually, although the change is measured in fractions of a degree per year and is typically inconsequential.

I really should apologize for the snarky comment about Dallas-Fort Worth. I spent way too much of my childhood in Dallas. Happiness was Big D in my rearview mirror.