Definitely equal thickness bud. They don't work like glass at all, and if you try to taper the limb thickness, you're going to end up creating moments (a point on a line being stressed with a load that is where the greatest amount of rotational force is) or hinges for ease of explaining, either at the riser, or at your tips.
Granted, with this art, you can try anything, but it seems like a murphy's law thing. Good luck! Pyramids are awesome!