I'm going to make a suggestion from Master's of the Bare Bow III. Do some blind bale shooting (no target, just a blank backstop). This should be from about 3-5 yards. Experiment with the grip. When you find one that is right, the bow should kind of jump directly at the target. As Overspined said, I found that holding the bow with a different grip than I had been accustomed to was the ticket for me. It also rotates my forearm so that the bones are aligned vertically. This not only give me a more solid bow arm, it also virtually eliminates string slap.
As to the vibration, a skinny string of D97 or such like will take care of that. I use 6 strands on my Kanatis, but shock was never an issue with them anyway. I have an 8 strand on my Mahaska, and it WAS shocky. Now it is dead in the hand and fun to shoot. Just make sure you pad the loops and build up the serving to fit your nocks.