On the horiz and vert stabs for my 1/2A Pylon Racers I trace out the outside pattern on a piece of 16th contest balsa. Then I cut strips of 64th ply maybe 3/8" wide, glue these onto the 16th balsa following the traced out pattern. I'll leave gaps in the ply strips wide enough where ca hinges are to be installed.
I'll glue this down one strip at a time with thin ca pushing down on the strips with the edge of a metal ruler against my glass table top. This keeps everything perfectly flat.
I'll also put a few small pieces of 64th inside the framework in a spot or two and solid 64th where it will be glued to the fuse.
Then I sand down the 16th balsa with the 64th framework glued to it until the bench sander just touches the 64th ply.
Then using medium ca I glue this down on another piece of oversized 16th contest grade balsa and then finally trim that down to the 64th.
When I shape the LE and TE down to the 64th ply it leaves a razor sharp edge.
The hinge slots are now already in place.
Sometimes I'll do the horiz stab and the elevator at the same time, shape them both together and then cut the ele off and sand the bevel into the LE of the ele.
I don't think this is any lighter or heavier than just a piece of 1/8" but it does make a nice sharp edge and as said the hing slots are already done.
This is a lot easier to do than it is to describe and it comes out strong, stiff and flat.
My 1/2 a horiz stabs are 10" X 3" including the Elevator and they all seem to weigh in at 0.3 oz.