How to build a trim tab:

Start off with a piece of balsawood. Cut a groove in the center of the slim side and glue in a piece of plywood. Then shape the base for the compensation weight from layered spruce. Mind that it is conical! Join the plywood block, cut to conical shape with the spruce stringer, attach both side stringers, the conical top and bottom ribs plus resocell end blocks with bronce bearing inserts and the weight base before adding  the preshaped plywood cover.
The tab is finsihed!

I am amazed by the depth of detail of this construction.