Yes, Peter, you are right, the LR masks work. I tried them on some Q2 sample RAW images (thanks Mike). I did find that if I pushed sliders quite a way a halo could appear round a selected object so there may be a limit to what you can do. Sky selection worked well even if there was a jagged skyline or the sky was in more than one area with an object between the camera and the sky.
I also tried a field of view calculation on the preset camera crops assuming the subject was 15 feet away. Even the 75mm crop seems that it can be printed up to 10.5" x 7" at 300dpi, and the 50mm at 15"x10"
Lots to think about, including money!
Jonathan