So far... it is looking like Black Locust is pretty close to Purple Heart, for me. When plugged into the same topper and condition the same. They play and sound similar. Not an exact match but close enough that I like it. I can not say I am surprised. I may have even said it already my hunch was Black Locust was high on my suspect list. Based on the Janka ratings, densities and grain they are fairly similar.
I have not been able to try all the suggestions yet. I have tried Hickory, Oak (red and white), Black Locust, Maple, Walnut, and Cherry. I will have to keep trying these as it quite apparent that all dowels in the same species are not made equal (I think someone already pointed that out).
I still do not have a way to quantify any "Results". So I am just going to keep on trying things and posting what I think.
I am going to try a third email to Dowels On Demand right now. I hear they have a large order going on at the moment that they are filling but I have not heard from them. At all lol. I guess the fella has the market cornered as I keep trying.