I've never modelled a stack before. I have successfully modelled yagis, and in this case, I want to model a stack of two Cushcraft A50-5S yagis, spaced 1/2 wavelength apart, with the lower yagi being 40 feet over real ground. I'd appreciate being guided to some good references regarding stacking before I get in too deep :~) 73, Bert, N4CW