How would/does it look with hundreds of images in a pano?
Thumbnail have fixed size, so the preview will scroll if it's bigger than the windows.
Do the thumbnails scale depending on number of images in the array/matrix?
Can the user choose the size of the thumbnails?
No. If you need such a feature, it's really easy to code.
Is there any value in having a gap between the rows and columns?
That's just to have preview, I don't simulate exactly the view. So I've put a 10 pixels gap between rows / columns.
Do we need to see the Y/P values in a title 'bar' on each image?
I think so because it's not necessary organized in matrix mode.
I think you've said you will fix the orientation of the images?
Yes, that's an exif decoding issue for the canon 20D only.
Most importantly - using this data does APP now manage to place (and stitch) correctly relatively featureless images that previously would have been 'orphans'?
Yes, pictures which are orphan are directly well located. The others are cp located. BTW : knowing the location helps me to find possible link between picture before launching the detection. So the detection is even better.