Im with blackbird, I'd rather ride on my cut springs than mess with some wierd bracketing to change the angle.
And thats another thing, youre changing the shock angle...Which means the force isnt being fully put on the exact top and bottom of the shock. The swingarm is pressing the shock more sideways instead of "end to end"
I wouldnt be surpised if the shock piston got kinked a bit with the right kind of bump.