One possible work-around is to create an approximate grid flight with CCC waypoints.
Then use Tuna's UAV Toolbox to adjust & square up the grid waypoints.
Then fly the mission with time-lapse stills.
No worries in an open flat area.Why bother with the time to fly an initial flight, unless one does not trust the maps.
Create the grid using toolbox from the get go. Easy enough.
[emoji41]
Jeff
P.S. have personally used this technique many times.