Nigel, thanks for posting that tutorial. I don't use Magix, but I do use Pinnacle Studio and this prompted me to try creating a mask video in Pinnacle. And I did it.
1) Put green screen video on main track.
2) Crop, size and use chromakey to removed the green
3) I used a tool called "Tint" which is part of the RTFX Volume 1 which is an add-on, but at times it has been quite cheap - I bought it several version ago and it carries forward each time. Anyway, I checked..change all black to white and change all white to white. Then I adjusted the slider to 100%. I have no idea why this worked, but I ended up with a mask video.
I rendered mask and chroma video, converted in popvideo and loaded into Iclone - worked perfectly.
There are likely other ways to do this in Pinnacle, I just need to fool around a bit more. Perhaps there are ways to do this in many of the cheaper video softwares.
"Wise men speak because they have something to say; fools because they have to say something"