I think only Schott would characterize this jacket as being "lightweight".
It is a substantial jacket, and if you are like me, a first time Schott buyer, you will probably be pleasantly surprised by just how heavy this jacket is. The suede that it is made out of is unique; I have never seen it elsewhere. The jacket feels well made, and it fits ... well it fits as perfect as someone with short arms would expect it to fit.
I usually wear a 44R in suits, and a 16.5, 32/33 is dress shirts. The only fit guide recommended a size large, and it basically fit perfectly. The shoulders were right on, and the bottom of the jacket just closes about my lower waist. This jacket does not have bi-swing sleeves (it would be great if the next iteration of it does!), and so when I raise my arms to shoulder height and bend them, it feels tight about my upper shoulders. I expect this go gradually go away as the jacket starts conforming to my body.
Overall, a beautiful jacket. I would strongly recoomend.