The plans say to "locally bevel" the counterbalance skins to smooth the transition with the rudder skin. What the heck does that mean? Not sure exactly how much to bevel, how thin to make it, etc.
They want you to just bevel the edges where the CB skins are touching the 903 tip rib and the spar. The CB skin goes under the rudder skin. A little bevel in those locations helps keep the CB skin from creating a hump under the rudder skin. Taper back about 1/2 to 3/4" with a file or belt sander. It needs only to be as wide as the flanges of the rib and spar. It helps tuck the skins in so a ghost does not show through the rudder skin after they are riveted.
Some builders have placed the CB skins on the outside of the rudder skins. I do not know if there are consequences for doing this, but I have heard of rudder counterbalances that came loose. I did it the way the plans show. It looks nice and is still on.
I looked at this a couple of weeks ago and looked again and finally said "screw it" and decided not to do it. I noticed no ghost and everything looked great.
Not sure if this helps, and not the best picture, but you can see the discoloration on the counterbalance skin where I beveled it (a little) using the Scotch-Brite wheel. It looks like I did it the for the entire overlapping area, but IIRC you are primarily interested in where the rudder skin makes the jump from the spar to over the CB skin (above the circled #2).
If you put the counterbalance skin on top, you will have a larger (longer) edge of thicker material exposed rather than the small edge of the much thinner rudder skin.
IMHO, don't overthink this, beveling the edge takes just minutes, and the rudder skin sits extremely flat. Build it per the plans... just my $.02... YMMV.
