What is the best airfoil for Edge 540 Style Aircraft?
For the Extra 300 which has symmetrical airfoils:


Extra 300, image by Ampbomber (source: rcgroups.net)

From the service manual of the Extra 300S:


Wing: from MA 15S (root) to MA 12S (tip). This change in profile allows for good performance both at low and high airspeeds.
Tail, for the 3 surfaces: - Wortmann FX 71-L-150/30


Wing airfoils characteristics seems not available online. On X-Plane.org forum (How X-Plane Uses Reynolds Number), it is suggested to replace the airfoils by NACA 0015 and 0012.

For the pitching moment coefficient Cm:


Cm is null for a symmetrical airfoil (no camber).


Manufacturer manuals:


Maintenance manual, in particular the chapter for the wings
Pilot's Operating Handbook.


Similar project:


On SourceForge: Building an Aerobatics Aircraft for JSBSim: The Su-26.




As an additional information, a study was conducted to evaluate the lift coefficient of the wing (or maybe with the tail) and the lift / drag curve, at a reduced scale:


Experimentally determined drag polar and lift curve for the Extra 300 (Figure 7)

However:


The scale change introduces a different Reynolds number, unknown adjustments must be made to extrapolate to full scale.
The curves are incomplete (alpha max undetermined).
The L/D ratio close to 2 is very low compared to the actual performances.