I agree with the scope centered over the cylinder for looks and balance.

If you want to "split hairs" these are my opinions:

1. Scope over barrel will help a little more to suppress barrel flip under recoil...

HOWEVER

2. There will be more abrupt forces ie. more G's of force transmitted to the scope and rings in that position.

3. Felt recoil will also be greater due to that extra mass further forward moving upwards.

As I said this is splitting hairs but if you watched the slow motion video I linked to a while back, it is amazing how even the scope tube FLEXES under recoil; the G-forces are very real.