I don't know that this is useless information. How much it is likely to impact a bowyer's actual decision making I don't know...I would bet as Pat suggested that people will use the staves they have regardless. But looking at return rate with given mass slats will give some information about the energy storage, I don't know that it is necessary to invoke harmonics. The more energy stored the faster the slat will overcome momentum and return to rest.
Also, while wood is not a completely homogenous material, trends within a species may be clear even after a relatively small sample size. I would not be shocked to hear that a certain species had values that were all pretty close to each other whereas other species may be incredibly inconsistent. Which are which may be of some value, and of the inconsistent samples did the better cases have anything in common-like late/early wood ratio?
Are there a lot of variables that may impact the results? Sure. Does that mean that trends will not show up or that people cannot look at the slat dimensions and make some educated guesses about how or why the slats behaved the way they did? Not really. I am interested to see what comes of this.
Huisme, are you planning on testing hop hornbeam? I would be curious to know how that stacks up against some of these other woods.
SOM