If you are going to blend a CLARK Y into a symmetrical airfoil I suggest you put the more cambered airfoil (CLARK-Y) at the tip and give the wing a couple of degrees of wash-out. In this way you will get a wing with very nice stalling qualities. The washout is needed because the cambered airfoil has a zero-lift angle of attack that is below zero whereas the symmetrical airfoil has zero lift at 0 degrees.
Or if he leaves it the way it is, he doesn't need to add washout because the wing already has aerodynamic washout due to the change in zero lift angle between the cambered root and symmetrical tip.
-David