I have bought several jackets from Aero and SB and can tell you that the patterns are not at all similar in fit. The original Calder Aero patterns are based on an English drape cut used for tailored suits. I imagine Ken was trained that way. They have high armholes with a large chest and extra room in the biceps. This is a typical Savile row cut and provides a certain level of comfort but today people want a slimmer look.The main difference between Aero and AL's patterns, the ones that they stole at least, is that Will changed the size tags so that 38 was tagged as a 40. Meant that they were automatically 'slim fitting', or as AL would have it 'vintage style with a modern updated fit'. There was a forensic examination of an AL jacket by a Heriot Watt lecturer, and right down to the internal stitching, she deemed it to be nigh-on identical.
None of the SB had the big chest and bicep so I had to size up to get the fit I wanted from SB.