Yup. The problem is when the stroke gets that long you are out of plenum volume and out of runner. You lengthen the runners and you give up plenum. You can put a spacer on it, but when I tried it, the BSFC went through the roof and I always has 2 lean cylinders, always opposite each other. So 3 and 4 or 5 and 6. It was a nightmare.
I think you have some options. A cam with faster ramps. Reduce the LSA a bit. And a single pattern cam. Hell , maybe up the intake 10* so you would be 270/266 and pull the LSA in a bit. You can't get enough intake to it.
