Thicker airfoils are stronger to flexion and twisting, but they produce more drag.

Switching from cambered airfoil (flat bottom) to uncambered (symetrical) will give less lift and less drag at the same speed; hence, your model will have to flight, to stall, and land faster.
Also, the relative angles of stab and wing will change, since your new wing will not have the pitch torque that the original wing produces.