I used Vicki Keene's service at http://keensights.com/index.html
Good turn-around, excellent quality and they have about every option you can think of to tailor the rib to your shotgun. I also let them install it since I am all thumbs, have no vise or other tools. Glad I did.
I have installed 5 or 6 keen ibs over the years on different guns with no issues.I don't know about you guys,but I wish that more trap gus would come standard with a little more drop from the top of the rib to the top of the comb to prevent having to need add on rib to increase drop,which is why I get them anyway.
I have Keen Sights on three barrels. I used them on my Kolar to adjust POI and on my 90T just to raise my head. Great people to work with, great product, easy to install.
Nice thing about using Keen Sight is they'll work with you. I told them what I wanted changed on POI and their recommendation and knowledge made it work.
Another feature is they will taper the ribs height to your needs and taper the ribs width to match your existing rib.