Those motors should be plenty. The important part of a twin is the distance between the prop tips. Not sure what the formula is but my rule of thumb is 1/2 diamter of the largest prop you will use, this would become the measurement between prop tips. I would build with no thrust and then shim the motors to have a bit of outthrust (toward the wingtips). I would do my test flights with motors at 0/0 though. Maybe an experienced twin designer could chime in on prop seperation formulas for models.