I am certainly
interested in keeping the weight down, especially aft of the CG.  You
mentioned forming a "small dam" to help reduce the chance of migration
of the epoxy/flox on closing.  I do not know how to do this weight
saving technique.

John,

 

The idea is to minimize the weight of the trailing edge of a control surface so that more weight isn't needed ahead of the hinge line to balance the control surface.  Your kit should have some white foam (1/4") available.  It is easy to cut a sliver of this and hot glue tack it 1/2" to 3/4" forward of the trailing edge (TE).  It can be sanded so that the TEs would come together as they would when bonded.  When flox is then buttered on aft of the dam and the parts are clamped together, the squeeze out will exit the seam and not just ooze forward inside the control surface.  In other words, the excess will not get past the dam.  Note also that the dam allows the flox to be squeezed under a bit of pressure rather than just oozing forward, ensuring a better bond.