There is a small shadow ~ 2- 3" at the top, but which is not readily visible, unless you're ~ 4' tall. There is a shadow zone in the corners which I could have largely eliminated by having 2 bars perpendicular to each other.

I mounted the lights using the standard flat clips. No angled clips. I toyed around briefly with the idea of using angle mounts, then decided against it.

I have flat bottomed cabinets. All the bottoms lined up perfectly and there are no rails underneath.

I have ~ 3" - 4"( sum of space from both edges) that the lights do not cover. I don't think it really matters.

The extent of the shadow zones you see depends on geometry.
1. The depth of the undercabinet space. The more vertical depth you have, the greater the shadow zone.
2. Angles. A corner usually is ~ 90 degrees. The temptation is to place the light bar on the hypotheneuse. Doing so would increase the distance to the furthest end of the corner.
3. Horizontal distance from the backsplash.

Thanks! I will try one and see what happens. I have recessed bottoms, but my GC said he would cut through the rails between cabinets to help avoid the gaps.

Fingers crossed!