Thanks for this new discovery! ;D The linked text says interestingly:
"No definite explanation can be given for the failure of the vee tail surfaces which a priori (because of the absence of interference) would be expected to lead to favorable spin behavior. The reason probably lies in the additional yawing and rolling moments due to side slip caused by the pronounced dihedral of the tail surfaces; however, their effect cannot be determined in detail."
I am going to create a Twin-Me-210 Twin-Vee (for the what-if forum)... Pleasant addition, tahnks again!