Where did the pistons come from? They are custom by the part number I think.. (sorry, just noticed you posted the tech sheet for them...lol) what confuses me are two things.. The valve reliefs are normally around 7 or 7.5cc, so I get that.. But the sheet shows a dish of .029"? Is there any dish in them? They sound like a set for a shorter deck block. On top of that is the deep cut chamber. So you have no quench. If the heads were on the block with no gasket you would be just within the range of any benefit. As far as compression, I ran your numbers and got 10.4:1. But something else... The MP gasket will wear a groove into the aluminum heads over time... You need to run a pre-flattened fire ring such as the Fel Pro Performance 1008. That is .039" compressed, and that will lower the compression to 10.1. The dynamic is estimated but the cam is small. So you will have higher pressures. I'm showing either 8.5:1 dynamic for the 1008 gasket, or 8.78 with your .024. In either case, with no quench, even with the aluminum I think you may be on the verge of detonation. I think I'd say go up one cam size to the XR280R. I think that will drop enough cylinder pressure to keep it safe.