In order to ultimately guide the synthesis, an understanding of the properties of D4Rs, along with an accurate description of the distribution of germanium atoms inside the zeolite framework is needed. However, the relative stability of various substitution positions and the degree of germanium incorporation into the D4R is not definitely understood, nor are additional factors, including the generality of this preference across zeolite topologies, the role of the Si/Ge ratio, or the effect of D4R asymmetry on the occupation of D4Rs.