With this maxIso thing it seems to work. Tried 2 clips, OFF->ISO3200 (shown in liveview and in clip) and ON->ISO800 (in both).
But if I remember right, I saw that in past - the liveview showed e.g. ISO800 and it was ISO640 or something. It seems it shows just the 100,200,400,800,1600,3200,6400 in liveview. Is it that what you mean?