My question is have you tried any choke tubes beside a IC?
I have shot the LB, and Fed. 2 oz. with a turkey choke, and the LB out did the 2 oz. with a .650 choke.
The IC is a open choke, and trying a tighter choke will be helpful.
And one other thing, like I say just cause your gun shoots the 3 1/2" shells, doesn't mean it likes them.