I wonder if the intention of the Death Star trench was to mirror some prior anecdotal experience Luke had flying through canyons on Tatooine - that would indirectly equip him to fly in those conditions.
I know none were filmed, but were any Skyhopper scenes (that he references in the deleted Biggs scene) ever considered or planned?
I guess in its absence, we will always have that first level on REBEL ASSAULT - or this thing https://youtu.be/O1NpZxn860M?t=1m10s