It isn't a matter of random choice, but of necessity that will dictate which kind of housing you use.
With a curved housing installed, close your eyes after looking at any kind of object at eye level, raise the pistol to eye level and open your eyes without moving the pistol. If you are aiming OVER the target, install a flat housing and try it again.
If you have a flat housing and the pistol comes comfortably to rest aiming UNDER the object, install a curved housing.
There is no mystery about it; you have to use the housing that best adapts to your hand and grip without having to bend your wrist out of line. This will make the pistol point more naturally, and produce better scores, especially in rapid fire.
Just thank the gods on Olympus that we have a large number of aftermarket parts available, allowing us to fit the pistol to our individual physical characteristics.
[This message has been edited by John Lawson (edited January 13, 2000).]