Take this with a grain of salt as I haven't built or flown a Micro Pitts but we can talk in some generalities.

For the micro sized airplanes with 12 inch wingspan - as long as you keep the wing loading really low - your model should work fine with the 0 cambered airfoil sections with 0 thickness. I have several flat airfoil sections winged models that work fine.

The original cambered wing is going to be a little better upright and while putting around will handle a bit more weight (maybe) but the airplane with it isn't going to be worth beans as a ARET maneuvering airplane. If you can make the airplane a lot lighter it should fly better. It probably isn't going to be as slow as the undercambered wing is though, there are some drag differences.

Keep in mind that the Tensor 4d is a much bigger airplane and can handle more weight better. That 12 inch span is pretty darn small.

However, back to the original question, going from the undercambered section wing (flat sheet with curve formed in) to the same airfoil with the bottom filled in with thin sheet isn't going to do what you want it to - I think. That just gives you a semi-symmetrical section which is just a medicore inbetween. It will be lower drag (and heavier weight) and so will need to be faster in flight than either the undercambered or fully flat wing and has little or no aerobatic capability.

So use the airplane design as is except go to a flat wing airfoil section top and bottom set at zero degrees incidence angle. Try to make it lighter though.