Parallel Valve Variants?

[claycookiemonster]

I thought I'd initiate a thread to explore the cost/benefits of the new "stroker" parallel valve engines. I'm building an -8 and am firmly in the parallel valve engine camp because of weight and CG considerations, but that weight consideration doesn't seem to limit engine size or horsepower anymore.

I'm not suspicious, but, like the saying goes, "If it seems too good to be true, maybe it is."

Are the 370/371/375/390/400/409/etc variants really just a matter of bigger cylinders? No significant weight increase? No other drawbacks? Any strange vibration or resonance or power pulse issues? There's got to be more heat, right, so cooling considerations?

If it's really this simple, why didn't Lycoming do this years ago? If it's really this simple, why the huge price increase to put larger cylinders aboard?

So; maybe it's not as simple as I imagine.

I'm not asking the moral question, "Why would you want to...?", that's another valid question for later. Right now I'm more interested in the engineerlng: is increasing displacement and horsepower really as simple as more cubes via larger cylinders/pistons and does this increase really come with no drawbacks or other considerations beyond the cost of different engine components and perhaps some slightly increased fuel flow?