The attempt to create the trim tab gap seal ultimately didn't work to my satisfaction. It wouldn't fill the gap at full down deflection, and then allow full up deflection, as its leading edge would interfere with the elevator trim tab spar. After looking and looking to no avail, I decided to carefully draw out the existing configuration on paper, then make cutouts of the trim tab to run it through its full travel. What this revealed was that if I added about one quarter inch to the trailing edge of the elevator at the trim tab cutout I could shorten the gap filler, then it would both cover the gap at full down deflection and fit in relation to the spar in the full up position.
To further this effort, I removed a bit of the filling micro on the elevator, and added a strip of carbon fiber left over from trimming the elevator. (Never throw away such.) This was fixed to the existing skin with Hysol, and after cure backed up from below with 1 bid. Next I will trim this addition to about one quarter inch, re-attach the trim tab and adjust as necessary to accommodate full up travel.
