Hi George,
15 minutes for 1000 images ad still not fast enough?!? 
Does that include feature detection? If so, then it’s fast enough in my opinion.
What kind of resolution are we talking about?
Prior only means something like preliminary, which in my understanding means it will be used as a starting point.
There should be an option somewhere that the source is undistorted - don’t have a license atm so can’t check…