Keep your regular size!
I'm often in between a small and a medium, depending on the item, and this time I went with a medium just to be safe and make sure I had enough room. Well, thankfully the fabric is pretty stretchy and comfy, however, it feels quite loose on me and there isn't really any compression that would make me feel more secure to wear this without tape. Still love it though, but I think a smaller size would have been best for me!