Guy, I do not think this is going with the other. The High compression pistons, are also high. So there will be less space in the cylinder for the detonation.
If you are going to flow the heads, I think you must replace the old pistons in the heads.
Try to measure how much space you have in the heads before flowing.
You can let it measure by the cammes (camshaft).
But if wont, you may flow the heads for least 0.3 mm max.
If you have some time, I want let do this work by Bruno Scola. It will be double work, flowing the heads and twin sparks.