OK, so I got the two Aircraft Jackets I ordered from the Marrkt Sale today. I got the Sand and "Khaki" (more of a dove grey) colors both in size 48. After a good half hour try on session I'm happy with them. Initially I loved the look of the fabric and the colors. I particularly like the Sand color, but the Khaki is great too. As for the fabric, it's quite light and definitely a bit sheer though I didn't notice that until later. I'm fine with that envisioning how I'll wear them, but more on that later. The sheer doesn't bother me as I tried a striped l/s t-shirt weight top underneath and while you could see it I thought it worked fine. In fact until I tried something striped I couldn't even tell it was sheer with what else I had on. My one knock on the fabric if I were to have one is that it'll wrinkle a bit. Nothing out of control though and I have a steamer so that's fine. As for the details, I remember seeing those slide buttons on last season's model and remember wishing a few months back that the SS 12 version had the same. Well I'm glad it does, especially in these colors. Love the look of the snap buttons and they really go with the look of the garment. Definitely look more military. They can scratch if you nick them against something, but I'm careful with my stuff so I'm not worried. I mentioned this before, but I love that there is a double zipper. These come in sooo handy when you're driving or sitting down and on this coat it really is needed IMO. On to the fit. Oh the fit. I'm probably the pickiest person when it comes to how things fit. I'm a 33" waist, a Medium in a lot of US sizing, 42 in a blazer even though I'm a 43" inch chest (which actually works in the blazers I get, though I don't really button them). I'm a bit slim-stocky I guess. Well owning the Cameraman in a 50 and having thought the Smock Jacket was still too "blousy" in a 48 and knowing my measurements I was confident in the 48. Initially after trying it on I felt the same way, but I had they baggy t-shirt I wear around the house on. So I tried on a woven shirt. Still fine. Went to a chunky sweater. Too tight. That's fine though as I wouldn't do a chunkier sweater with this lightweight a coat anyway. Tried a regular cotton crew sweater over a woven. Fine. Tried that knit hooded top (which I wouldn't do anyway because of the hood but tried it more for the weight) which is between a l/s t-shirt and a sweatshirt in weight, still fine. The coat does taper to the waist as Turunen noted weeks back (I still remember this...), but sadly I have a somewhat flat ass and so it just works down there. However this is where the double zipper comes in handy for driving and such. Were it not a double zipper I would definitely not like the coat as much. I liked the looked with jeans and with my slimmer chinos it wasn't as good, but they're a bit stretched out and I'm getting new chinos soon anyway. Didn't try them with shorts, but I think they'd look great with shorts and as lightweight as the coat is and considering the styling details on the coat I think it'd work from a styling perspective. At the end of the day I could have ordered them in 50s in the same order and part of me wishes I had for peace of mind, but I'm sure I wouldn't have liked the 50.
So my recommendation on sizing would be to go down a size if you're slimmer or "average" and want it to fit "normally." The chest is roomier, though the raglan makes it seem less so. If you want it boxier then go TTS. Cabourn is true to what the originals were and so I think it's boxier for that reason. However for everyday use and styling and I would think that most people would prefer to go down a size. If you wear baggier pants though then go TTS. Oh, and I forgot to mention above that sleeve is roomy enough (not too baggy looking though) and you can unsnap it at the cuff, but I would caution against that as it looks a bit "like sleeve of wizard" if you will. 
Finally, I really like the look of the coats and am very pleased I got them. The final Marrkt price is fine by me for the coat, though I wouldn't have wanted to go much higher. While I don't think I would have liked the oilcloth, I really like the colors and look of the non-oilcloth. Again, love the snap detail and how it blends with the coat, it's hardware and the military look. Overall I really like the Cabourn SS 12 collection. I'm more of an AW Collection type guy, but this collection had some great pieces even though I only bought two styles (in multiple colors). I think the SS 12 collection has a lot of longevity in terms of a heritage look and colors that one wouldn't get sick of and that's what I was looking for in the garments I got.