As someone who runs very, very cold (I wear long pants in August all the time) I've tried wearing tanks under my shirts to make them warmer. "Clever," I say, "I'll be warmer and no one will be the wiser." And yet, this rarely works. I have a number of tank tops too tight to worn by themselves which I use for layering, but they inevitably ride up my waist and add bulk. I'm thinking if I bought them even clingier, they might stay where I put them, but I also wonder if my massive waist to hip difference means that they will always creep onto my waist. For reference, there's about a foot of difference there. Thoughts?