OK we've got below the baffle, above the baffle, right on the baffle so far, how about right to the top.��
Helpful advice, isn't it? Actually, they are all correct, to a point.
I just helped a new Model A owner with this very question this morning.
He is lucky. He has a second hole in his baffle (in addition to the one that the overflow tube comes up through). So I was able to show him where his coolant level was through that hole.
When the engine is hot and running at an idle, coolant should be just at or over the baffle, but not by too much. A little bit under the baffle will not hurt anything, as long as you can see coolant.
It is really hard to get the level right when the engine is cold, if you can't see under the baffle.
If you overfill the radiator, it will puke the excess out when it is hot and you are running down the road. Don't panic when it does. And don't "top it back up" or it will just do it again the next time you drive. This is the system "seeking it's own level". Now, if it boils over vigorously, you have a radiator problem.
If you can't see any coolant at all when the engine is hot and running, add a little more until you just can. This is when hot.
Hope that helps.