Based on other plans the rear limit of the CG is just in front of the bottom wing LE.
There is a means to calculate a starting point for a Biplane. Looking at it from the side, measure the front to rear distance from the top wing LE to the bottom wing TE. Calculate 28% of this and measure that distance back from the top wing LE. It should put you somewhere near the thickest part of the top wing and almost half way from the LE.
For the wires, based on the size of the model I would say most definitely. At least do the flying wires (the ones that go from the lower fuselage to the underside of the top wing.). But I think you really need all wires. The alternative could be so much scrap.