Semisane, I have never been able to use those , fiber optic sights and get a good group, a Williams peep a good solid old fashion front sight or a ghost type of my own making and two and a half inchesare possible.
Now there are some things that we some times use in combination that work and we don't know why or if its coincidence but if I had your circumstances to deal with I would try a greased wad over the corn meal because that's what has worked for me before, I my TC's I have to use a dry wad under the corn meal and a greased wad over the corn meal. Lee