I'm considering ordering my first jacket from Aero, namely the slim fit version of the Motorcycle Jacket (known as Ridley) and have a question concerning the chest size. My chest measures almost exactly 38" (c. 38.5" when layered) and I'm torn between the sizes 38 and 40 (with 20.5" and 21.5" chest measurements, and allowances of 3" and 5", respectively). I'm of a relatively athletic build. Anyone with similar measurements, do you think the smaller size will allow any layering at all or should I go for the larger size just in case? As for layering, I'm not necessarily talking about an ultra thick wool jumper but something lighter to put on when it's colder. The jacket will be made of Aero's goatskin.