duky-
Don't panic. Your not alone. Of the 2D, DI and SI, I also struggle with the DI the most.
I have set at home watching recordings on Humviewer and while passing over a known target shown in
2D and SI, nothing or just a small part will show in DI.
I have had some very good DI screens, but everything has to be just right.
I think it has more to do with the correct angle, direction, speed etc. than the sensitivity adjustment.
The DI has 3 choices of display. Narrow,medium and wide. Mine is set to wide.