I am 50 Formosa (let out waist), new pattern FJ 52, FL I'm a L, and the HJ is 52. If I was skinnier/lost weight, id probably do 50 for HJ. For most people who are on the skinnier side, I'd say don't size up, IMO.
Thanks, FF! I probably agree it's the angle/my slanted posture in the pic. My Formosas tend to actually be on the narrower side (technically I should go with more structure in my SC since I'm quite boxy, but f* it. They're lovely SC, to say the least).