Brian,

Stiffness will vary from paddle blank to paddle blank. My favorite quartersawn cedar paddles are extremely stiff, with just enough flex and spring to make them feel lively. I have rejected more than a few though, that had good grain but were too flexible for my tastes.

I haven't had any trouble with cedar splitting. I am not very knowledgeable on lumber preparation but I believe that the lumber that I use is kiln-dried. Perhaps your supplier did not properly dry the lumber (kiln or air-dried). Or perhaps poor storage, allowing the dried lumber to get wet, has greatly increased the moisture-content of the wood. It is not "green" (undried) lumber is it? If so then you will most likely have shrinkage and "checking" problems.

The only problem that I have experienced with solid (kiln-dried) lumber, on very rare occasions, is that sometimes planing the surfaces will release internal stresses that warps the board. Chris Cunningham recommends using the "center" of the wood, planing away the heat-treated outer edges, to combat this.

If you are going to epoxy the ends, you might consider making them white, to resemble the traditional bone end-fittings.

Greg Stamer