It's good to be sceptical, belongs to the engineering mindset. The simulator is not 100% realistic, even though it comes very close if I have all necessary information/data. The airfoil data are always uncertain so I just compare several cases to see which parameters are important.
The contest T2 flies better than the Japan T2, no doubt, and no doubt due to the symmetric airfoil. I'm interested in the 35% airplane influence and not in the 65% pilot influence (sounds better than error), at least for now.
The tail wag was still there after the modification, it was just more
damped, meaning there was only one wag instead of oscillations.
Please check the carrier wing airfoil carefully because it is hard to see if a thick airfoil is really symmetrical. If you compare a 2415, 2419, and 2422, the camber is all the same (2%) but it seems less (or even none) the thicker the airfoil is. It's important because it makes all the difference. I just tried a NACA 2422 for the T2 and even if I set the airfoil parameters for a decent stall behavior (what this airfoil really doesn't have) the plane won't stall with normal elevator throw, only with kick-up (as any Taurus with a semi-symmetrical airfoil).
The problem is the 0-0 wing-stab setup Ed chose for the Taurus. Zero incidence is not zero lift for a semi-symmetrical airfoil, so there is some decalage (about 1.5 degrees). This requires the very stable setup (big static margin, forward c/g) and the stab has to work hard against this forward c/g
and the airfoil pitching moment. Without kick-up, there's just not enough elevator/stab effect left to accomplish a stall.
Seems this point is the most important. All others are not that influential, like dihedral, sweep, moment arms, and so on. Phil Kraft wrote somewhere that he tried several semi-symmetrical airfoils but was not satisfied with all of them, so he changed to symmetrical airfoils.