OK A "TYPICAL GLOW TRAINER" is a balsa frame with monocote covering. Usually a Kadet, Serioretta, or an Eagle 2.

If the H Stab is loose and flexing then the easiest fix is to;
1. buy some 1/4" triangular stick,
2. cut it to fit the length of the H Stab where it meets the fuse,
3. Remove the covering around the point of contact (all four points),
4. Glue the Triangular stock into place on the H Stab (top - bottom - both sides)
5. Recover the area to prevent fuel contamination.

This will strengthen the H Stab at minimal cost and weight.