RE: trailing edges
Tapered to a sharp edge will have less drag, but will be less effective. Squared off will create more drag, weigh a little more, will be a little stronger but will be more effective. How much/less drag and how much/less effective depends on a whole bunch of factors. Definitely do not round them. If you're going to make them sharp like the rudder of a glider, then laminate a thin strip of carbon in the middle of the structure.
-Ben