Right now, I have nine original MA-1s (I think). I'm not sure if I have a 1971 Alpha but I do have both a '73 Alpha and a '72 Alpha. Those two Alphas seem to be my longest MA-1s....especially the '72. I know, without a doubt, that they are my largest MA-1s. They are always the ones that I have to wear when I'm going through a phat phase, as I am now. I also have a '65 Alpha that is fairly large and long, but I replaced the knits on this jacket with G&B knits which are wider than originals, so it may not be fair to use this jacket as a guage. For a while I just thought that Alphas ran large. Then I bought a D-series '64 Alpha (with the C&C zipper) and it turned out to be short. Not really skimpy, but short. By the way, I'm not a guy who can wear more than one size jacket. All of my nylon is XL.
On the other hand, my B-series Johnn Owenby is my smallest MA-1...followed closely by my C-series Skylines. My Satellites seem to be about average in both size and length.
Just my observations, for what little they are worth.
AF