Welcome to the club of people completely miffed by the lack of an optional gimbal angle override setting. It's been a big hole in the features of DD for a LONG TIME.
Gary: Try fly manually for obliques when doing a 150 acre area for a topographic survey and let me know how that works out for you. (LOL)
DempseyCreekKid: Those two apps are for iOS. Some of us don't choose to live in the Apple World.
I'm a project manager and no longer a pilot but when we were testing apps a long time ago, I believe DJI Ultimate Flight was an Android app that alllowed you to fly crop-duster patterns with the gimbal at an angle. However, I believe you had to manually drop all the waypoints instead of specifying the area and letting the app calculate the flight paths. Plus it's a less updates not as well-known or supported app compared to the rest.
Does the Pix4D Mapper App support oblique missions that are not orbitals? I thought I read it's even more glitchy than DD though.