Dick, at lower speed like we fly I understand that the SQUARE blunt trailing edges produce less flutter than if they are rounded because the air will peel off the sharp edge more cleanly and then flow over a bit of a turbulent dead zone in the wake of the blunt edge. In effect the turbulence forms the missing trailing edge. That's also the Kamm theory I believe.

Rounded trailing edges can produce an action where the air tends to alternately lick over and down and then flips to over and up and sets up an oscillation much like a flapping flag. A great way to induce flutter of course and a good reason for keeping trailing edges blunt if they can't be sharp edged.

Selig's wind tunnel work from the original Soartech 8 showed that there were very real and significant drag reduction to be had by keeping the trailing edge sharp as opposed to even 2 to 3% square blunt. But of course that sort of advantage is only needed for speed runs with racers, be they powered or glider.

As I recall a flat plate airfoil produces a separation bubble at a very low angle of attack but that bubble then acts like an upper surface curve. It's been a long time but I seem to recall that a flat plate Cl vs Cd curve is very linear with a surprisingly high max lift coefficient but an almost direct drag cost as the lift rises. But as we are seeing on the right type of model that sort of charactaristic can be a good thing. In the case of 3D designs it allows the model to dump speed pretty much on demand while maintaining lift. Not a bad thing at all given the mission.....