I'm building an EPP F-86 combat foamie with coroplast tail surfaces. I'm considering gluing small wooden dowels to the LE of the stabilizer and the fin both to make the LE more aerodynamic and to provide a heat-safe surface for attaching the Ultracote.

I could do the same for the TE, too, but I'm wondering whether this will improve the aerodynamics of the glider. I think I recall reading somewhere that the TE of tail surfaces should not be rounded as this can lead to flutter at high speeds.

Any suggestions?

Leading edge dowels help aerodynamically and structurally, especially on wings.
The trailing edge, anything; rounded, tapered, squared off or nothing will work.

Since there are lots of mutually exclusive options for the TE, can you make a recommendation based on the following requirements:

1. coroplast tail surfaces
2. fin only, no rudder
3. oversized elevator
4. 48" wing span
5. seeking strength and improved aerodynamics, but only if the weight trade-off is minimal.

Given this list of requirements, would you go with dowels on the TE (for a rounded edge) or stick with the default squared TE coroplast edges?

I'd leave the t.e. square. This particular application isn't truly "high speed", where a thin as possible t.e. works best.
I've tried them all; square, round, tapered, and found zero dreaded flutter. That is created by something else.
Extreme finesse in aerodynamic improvements can only be seen for a plane where performance is measured... speed, endurance.
A manuvering airplane gets into so many areas where drag all by itself overwhelms any nifty streamlining that it's not worth the effort, for a plane with a short expected life time.