I always wanted a tapered rib on a gun exactly because of the effect you described. I have shot a few, and found it to be advantageous over the parallel rib.
Just recently, I've shot a 32" barrelled gun with a parallel rib, but with a central groove down it, which leads the eye beautifully (I normally shoot a 30" with parallel rib with no central groove). The 32" also has a smaller white bead on the end, which is giving me the feeling of a very long, and precisely pointable barrel. I'm finding the perceived lead I give can be cut back dramatically, and I'm tending to shoot in front until I get used to it. This is making longer targets much easier to judge for me, which are something I have struggled with in the past. Provided I can still shoot the close stuff as well as before, and so far it has been no handicap, I'm convinced I will pick up more targets that I wouldn't normally expect to hit.
Good result all round mostly because of the rib and barrel length. Oh! And the change from Beretta to Miroku. If the rib tapered too, it would be just about perfect though! :biggrin: