Thanks for the info, Hendrik...this helps me understand what is going on a lot better.
Now for my new report. I spent more time with the same 2 files and also some other files as well. Due to my haste the first time, I had a couple of things wrong:
1. "Checkbox" never worked on episode #1...I obviously remembered incorrectly.
2. Episodes #1 and #2 are NOT identically created/processed. I found this out by using CNTRL-J while the videos were playing.
Episode #1 is listed as:
Window - 3840X2160
Input - 3840X2160
Based on what you just told me, that indicates to me that the black bars are baked in.
Episode #2 is listed as:
Window - 3840X2160
Input - 3840X1600
That tells me that the black bars are not baked in.
The difference in these 2 files explains the difference in behavior that I am observing, and both controls are working correctly.
I tested about another 6 files with differing Windows and Inputs and behavior was now very predictable and consistent.
For my particular preferences with a CIH setup, "percentage" is the best global control setting due to the inconsistency of baked in black bars from one video to the next, but others might find "checkbox" a better solution...each person can take his choice, or may come up with a solution that combines the two.
This is the same setting as the OSD subtitle shift option - except now global and you can directly enter a number. Changing it to be different from the OSD would be very confusing.
This is not correct from the end user's point of view. The OSD simply uses the terms "Up" and "Down" and we have no idea whether or not the value is "+" or "-". I can adjust either way since I now know which is which, but I still think "+" values would be more intuitive to shift a subtitle upwards...It is of course your call.
Thanks again for the information and your hard work...these changes make me very happy and it is my hope that many other users will like it as well!