Go get yourself a set of Tru Glo Fiber Optics sights. Make sure they are the clamp on and not magnetic. Measure the width of your rib and they do make a set of clamp ons as I had them on my 11-87.
Also make sure they allow for Windage and Elevation ~ means you can move the back sight up and down or left and right.

The front sight fits right in front of your current shotgun bead - so there is no reason to take it off.

Patterning
I start patterning using trap loads. I use a cheap box as the recoil is less, the cost of shooting quite a bit is less as all I am trying to do is dial in my sights so I can punch out a quarter sized (25 cent piece) dot out of my cardboard at 10 yards. That is where I start.
When that dot is completely gone I move back to 20 yards to check my pattern. Still good? Great.
Now I switch to the second target on this link.
Link
http://lewand.tripod.com/turkeytargets.html

Now I will adjust my sights or my scope - both are really the same so I can consistently put the bottom center of my circular pattern at the point where the skin starts and the feathers stop on a turkeys head. Why? It is one consistent aim point that all turkeys have andis very easy to see.


The Picture I made is crude but what I am after is completely encircling the head with my shot cone. Once I am happy doing this with my trap loads I do switch to my Turkey Loads. I have found that I needed no further adjustments to my sight I chose at all.
I then shoot at 30, 40, and 50. My rule is 8 to 10 hits within the bones of the neck, skull or eye. All those are clean kill shots. Any less than that and I have developed my maximum range.
Not only do yo save ammo cost - you save yoru shoulder too.
One last thing - I do use a bench to develop the pattern - then go to my sitting position to use my turkey loads.

Hope that makes sense - Be Safe and Good Luck out there!

Dave......JW