Agree on the Empulse's splitting ability, and I'm doing it with the Brammo hard side cases. I have bar-end mirrors and I figure if they clear the car mirrors on both sides, the cases will easily fit under them. So far, they always have, even when I rarely tap one of the mirrors, causing it to fold inward.
Actually the only time I got into trouble with side cases was on my BMW R1200R when I wanted to change lanes with traffic stopped and caught the rear bumper of a car that I was maneuvering around and had cut the curve just a little too close. No harm done, just a soft bump. I didn't leave any mark on the car and it didn't on my bag. But wait, oh yeah, my ego was bruised!