Thanks, Raid, for the beautiful portraits. You didn't shot wide open, and indeed thise lens needs to stop down a bit for best results.
As for the size: the glass of both versions has the same size. It's the brass mount and RF cam which makes the lens heavy. (It's not bigger than a 35 Summicron 4th Gen though)
As far as I know, distortion is present in every 4- or 5-element Ernostar type. Probably there isn't enough room to correct it completely with this type. With 3 groups in front of the stop and one behind, it is not in balance which causes distortion. It was never announced for architecture usage.
The deep-bluish coating (like Voigtlaender, East German Zeiss or Nikon RF lenses of the 1950's) has surprised me a lot. I'm used to modern, nearly colorless coating which effects that you barely see the glass. I guess this is one reason for it's "warm" characteristics. Don't have it used with color slide film though...