Large rpm drop

It's easier to figure out something is wrong when using a flat top piston.

When you do the down fill you can easily calculate the valve notch volume doing that, and almost all the time they are bigger than advertised.

It a bit more difficult with a domed piston. But you can do it. It's also quite funny that dome volumes are usually not what the piston manufacturers claim. They are usually LESS that advertised.

That's why I don't like taking the word of the guy making the Pistons. They are wrong often.
OK, well I'd expect that if the eyebrow/notch volume is being deduced from the down-fill method, then some of that volume is actually from the crevice volume down by the top of the piston. That usually works out to 1-1.5 cc in the size range of these bores. I add that to the published eyebrow volume (or reduce the net dome-eyebrow volume for a domed piston) to account for that. Pretty much the same end result either way.