RE: Do I really need these?
No way. Go ahead build straight and have fun. By the time you are finished you will have a grip on where the center of gravity should be and control deflections can be measured with a ruler or tape measure. I built a wooden stand with the top curved(about 1/2 " radius)and sit the model on it moving it until it is level....that is where the center of gravity or CG as commonly referred to is.