Functional testing of SFF parts represents an exciting area of research in solid freeform fabrication. One approach to functional testing is to use similitude techniques to correlate the behavior of an SFF model and a product. Previous research at UT Austin has resulted in development of an empirical similitude technique to correlate the behavior of parts of dissimilar materials and geometry. Advances in the empirical similitude technique are presented in this paper. Sources of coupling between material and geometry characteristics that produce errors in the current empirical similitude technique are outlined. A modified approach that corrects for such errors is presented. Numerical examples are used to illustrate both the current and the advanced empirical similitude methods.