I think there is always a degree of hit and miss. I've bought two new jackets from Aero, sending in measurments and taking their advice on sizing, in the end neither of them fit me exactly how I would have liked (ones a little too slim and one is at least a size too large.) I still like them both but my best fitting Aero is one I took a gamble on eBay which had, I think, only a chest measurement and jacket size in the listing. Advice on measuring a similar sized jacket is always a great place to start, but no guarantee. I've got jackets where the chest measurement is an inch and a half less than I would expect to fit me, but due to the cut of the arm holes and the shoulders and such the jacket fits great. I think knowing that you might not get it spot on from the start is good and why a good return/exchange policy is something I always value when ordering a jacket.