After some head scratching about the nature of my previous failed attempts at building the trim tabs, i came up with the idea that i needed some sort of interlocking blocks that wouldn't slip around when i was trying to bend the close-out tabs on the sides of the trim tabs. Some judicious clamping and careful bending later, viola! it works!!

Then it was just a matter of riveting the hinges on the elevators, bending the hinge pins, and drilling a little hole that gets used to safety-wire the hinge pin. yay!!!