Doesn't call for making them, but they look nice and may save you some day going through a doorway. You can make them from wire like you use for pull-pull controls, or from Kevlar thread (the lightest method), or from 2-56 control rods with clevises on the ends, like Edwin says.

I like to use male spade electrical terminals and the 2-56 rod. Get the terminals made for 16-18 ga. wire, pull the little plastic piece off the crimp end, and solder it to the rod, bend them to the desired angle, drill out the tiny hole to a size that a #2 screw will fit through. Drill your holes in the H-stab, V-stab where desired (usually close to the rudder and elevator hinge line, near the ends); harden the balsa by wicking thin Ca into the drill hole, and put a small screw and nut to hold them. These are the braces I made for my WACO this way:

If you make them from wire or kevlar, they can be like these on my Bristol; Sullivan sells a tail brace kit that uses Kevlar.