IMO the standard comp achieves it's "sweet spot" around the 1.5 bar (22psi) boost range. After that it becomes increasingly difficult to tune and to make more power with the increased boost. Anything less than 1.5 bar of boost and you're just wasting power by going low comp. The sweet spot of a N/A 9.5comp cvh seems to be around 1.0bar of boost.

However, a lower comp will relieve rods from a little extra stress. It also will make the car sluggish before the boost builds, i.e. 1000-3000rpm.

To acchieve a lower comp, you need to leave more volume for the combustion chamber and there's a number of ways to do this.
-fitting lower comp ( pref. dished) pistons
-dishing the original pistons, there's quite much material on the crown really. Around 7mm.
-fitting a thicker head gasket
-fitting a separate de-comp plate
-machining the combustion chamber