I've got a CST mouse (complete with billiard ball, you can see it in my Twitter background @__mharrison__). I had the CST between the halves for almost 8 years

I've got a CST mouse (complete with billiard ball, you can see it in my Twitter background @__mharrison__). I had the CST between the halves for almost 8 years but recently went back to putting it on the right side. My conclusion is that there are general principles of ergonomics but in the end you need to listen to your body and adjust if you feel pain.