I build mostly flat stabs.  Usually a fake solid sheet tail for an OTS airplane.  I lay down a piece of quarter grain 1/32 and then build up the stab/ elevator outlines and a Warren truss (or what ever I feel like at the time) out of whatever thickness it takes to make the stab as thick as I want.  Then glue another sheet of 1/32 on top.  Weight it down between two pieces of 1/4 inch plate glass.  Cover with silk, silkspan, tissue, as appropriate.  Much stiffer than a solid stab of the same dimensions, and lighter (maybe).

I also build flat stabs. I learned how to do this from Les McDonald and I think folks like Paul Walker and Windy also build (or have built) stabs this way. If you build it right, it will be very light AND very stiff - one of Brett's major concerns.

I cannot say if there is any difference or advantage to either method. Brett's results speak for themselves, as do Les McDonald's, Paul's, Windy's et al.

I think it's easier to line up a flat stab than an airfoiled unit and think that is just as important as stiffness.

My two centavos. 

Ron

I build mostly airfoiled stabs. Aligning isn't too hard if the cutout in the fuse is straight and you use an incidence meter. I mostly build them because it's easier to make them very, very rigid and straight and because I imagine that the greater lifting surface it provides allows me to carry the CG further back, though I'm probably just imagining it.