How to keep stroke size consistent in Essential Graphics, regardless og text length?

How do I make sure the stroke size (and shadow) stays the same, no matter how long my text is?
Well, I draw a rectangle and select "pin to" my text in Essential Graphic, it works fine except that the stroke size becomes larger or smaller depending on how much my text deviates from the length which my rectangle i drawn. How do I make it stay the same?