Zeeshan,

Flypaper has it right. Shoot for a zero-zero thrust alignment and you'll be as close as possible to the ideal situation ... plus, it's easy to measure. 90-degree triangles are easier to find than 88.5-degree triangles.

You'll want it straight for hovering, of course. And in other 3D maneuvers, any offset will work against you as often as it works for you. There's not only the question of upright vs. inverted, but also knife-edging one way vs. knife-edging the other way. Differential thrust would simply add more confusion to an already complex set of interacting forces.

Ian won't admit it, but his "built-in left thrust" is probably a repair, too.

Dr. Simpleton