Keywords:Nonlinear modes, modal truncation, MicroElectroMechanical Systems, MEMS, macro-modeling.This paper reviews and verifies a methodology for nonlinear modal truncation especially suited for extraction of quasi-analytic macro-models. The method is very well suited for analyzing problems expanded by Taylor-expansions. Two systems are tested. One arbitrary system and one macro-model of a MEMS 'butterfly gyroscope' built from elements of two nodes and 12 degrees of freedom. Errors from the truncation are identified and scaled, and vounrabilities are enlightened. An approach utelizing the method for modeling biased electrostatic forcing is suggested.