Pete,
The best way to determine baffle height is to experiment--with the powder you want to use. The best height will vary not only with the measure but the powder.
In general, it works to use a smaller powder measure for smaller charges, and a larger one for larger charges. I have several for various purposes, including one of the Lyman 55's with the Homer Culver micrometer conversion that Ken Oehler very generously gave me a few years ago. For many years that was the preferred measure by short-range benchrest shooters, and it still works VERY well.
The other side of powder measuring is that charge weight doesn't always mean consistency, since powder weight for a certain volume can vary with humidity and storage. Each time you open a jug of powder it can either gain or lose weight, due to humidity. It can either gain or lose weight, sometimes meaningfully. Weighing the same amount of powder many NOT result in the same results, while volume may come much closer.
Which is why proper powder storage--and leaving a container open as little as possible--can make a difference in velocity and consistency. However, whether this matters or not to most handloaders is another question!
