I saw your post of this in the Maschinen Krieger forum, but it's even better here to see your progress pics, Momo!  This is a beautiful conversion!

I built my first Gustav a couple of months ago, the old Nitto kit.  I assembled the suit with the pilot separate, so I could paint him.  I figured he'd drop right in when the time came.  But I found when I tried to fit him in, that he didn't fit between the arm holes!  I had to file down the sides of his torso till I could slide him in.  Did you find that with this kit, or did Wave engineer it better?