Best way to deal with this issue is to live-fire it at the range. Get yourself a blank target backer, stick a clear aim point on there and try out different cants at various ranges, marking your groups after each run.
I did this and it's very enlightening. It's one thing to read about what happens, another thing entirely to storyboard it out.
This also applies to seeing the deflection from resting your barrel on/against objects or barricades. At 50 yards, a center chest hold with the barrel resting on the barricade can cause rounds to be over the head.
Great visual tool for teaching classes also.