I have used maple, poplar, and poc. I cut a v groove in a piece of plywood to hold my 3/8" sq. stock in place while I use a small hand plane to take off the corners to make an octagon shape dowell. I then take off the 8 corners to give me a 16 sided piece. From there I sand the shaft down to fit through a tru-center taper tools shaft sizer(??). By running my shaft through this, it will leave a shiny spot on the wood that shows me where more wood needs to be sanded off...You can cheat by chucking up the shaft to a drill and run it through some sand paper (this method will leave some unsightly cross grain scratches), but speeds things up a bit.
You can sand out your shafts to get the spine your after with any wood species, but the more ya sand out you'll get a bigger variation on weight. Just start playing with it and the rest will come to you......good luck....Terry