Over board with File fit rings
Few books take into the fact of the design of KB pistons which I'm not sure that Joseph may be running but it sounds like he is. They have the top ring grooove moved up higher on the piston. Then the ring gets hotter and expands more so you have to run a larger ring gap. Joseph I did exactly what you did when putting mine together. I knew the machinge shop owner real well and went back there to buy one set and they just gave me an extra top ring. He said most of the time they have extras laying around. If you know your shop well you may try this. If not one piston ring set don't cost much.