Recently did my 4 element siro.Best just to scale it up. Element length is also dependent on spacing , element and boom diameter,and how the elements are mounted and driven. Unless you can copy all that it's safer just to scale.Try one of the modeling programs ( I use yagi cad, it's free and it works)it will show you if those setting work. Multiply length and spacings x .96 will get you ball park ,and you may have to adjust the gamma match