Coosa;
I will have to say it is not the most Aesthetically pleasing gun I have ever looked at, but if it works & you like it that matters not.
Not sure though just what you are referring to when you say it had to have a double taper. Are you referring to the fact it had to taper both horizontally & vertically. This would seem to me to be a simple taper in each direction which should not present a problem to a reliable maker.
A double taper would to me indicate that the taper changed in the same plane, but I see nothing that would indicate this to be case here. I don't recall the length of the barrels from your previous post but if they are 30" then to taper from .410" down to .250" would give a taper of .005333" per inch. If this is constant for the length of the rib then this would be a single taper.
Just Clarifying, but I "Think" what you are referring to is Two Tapers (IE one in each plane) rather than a Double Taper.
You are correct, and I just worded it poorly. Saying it has two tapers would be the correct terminology. It has one taper to fit the original taper of the rib, and another one to correct the POI. And while you are right that it should not have been that hard to make, I've had so many bad experiences lately with people unable to carry out simple requests that I am surprised to get something back that was done correctly. They got the Bradley front bead right in the center of the rib too. You would think that anyone could accomplish that, but not so.
The 3/8" height at the rear definitely doesn't fit the lines of the gun. They say they can get as thin as 1/64", so I could have gotten by with just 13/64" at the rear. That would have looked better, but it would have done nothing to help me with the fit of the gun. As I said, I got the idea for starting the rib at the end of the monoblock from the 626. Here is what it looks like for those not familiar with it:
hosting pictures onlineKeen Sights could have made the rib to look very much like this one and correct the POI issue. They would have glued on a front bead if I had chosen this option. As it is, they were able to thread it.
Again, this is certainly not for everyone or every gun. This was an $800 shotgun. When I am dead and gone the next owner can pull the rib off and throw it away, and the gun will look the way it did when Beretta made it. But he better learn to aim high, and it would also help if he doesn't have a neck.

Good shooting to all.