You should just always use a RBF so they never have a clue what you're thinking.
My husband has one. Friends will ask "Is Mr RLD upset?" I look over at him to see, "Nope, he's having a good time and enjoying himself!" I finally bought him three t-shirts:
"I'm not angry, this is my Scottish face"
"This is my happy face"
"Dutton Train Station Tours"
We knew our son's GF would fit right in when, the first weekend we met her, my husband mentioned to her that he enjoyed the weekend and getting to know her, hoped she also enjoyed it; then explained he knows that sometimes he can be a little intimidating, but he's trying to smile more and hoped he didn't come off that way with her. She just laughed and said, "Well....I did notice you have a very impressive RBF!" Yep...she captured his heart!