Just thinking outside the box today

As i read this post, i see the merit in going to the 8mm valve stems. PR, IMHO your own eval of this move is important because you would have control over the whole test, as well as rhe ability to try any tweaks that may give added results. So many questions come to mind . Maybe extra flow from 8mm stems might only gain 5 to 7 hp?
But a couple hundred more productive rpm up top might allow an average of horsepower to go up even more. I would assume this might be more true on a motor with lots of flow available per cubic inch, versus a head limited combo?