In the multiple control input, multiple controlled output system controller design process, it often happens that control providing acceptable performance can be obtained with a more simple control structure than that of full state feedback. The question that is addressed is whether or not one can rationally and quantitatively establish that such a simplification can be validly used in any design situation. This question is highly relevant to the design process because ignoring irrelevant details of a system reduces system development costs. To a large order, the answer to this question has been provided by perturbation theory; both singular perturbation theory and continuous perturbation theory. In this paper we demonstrate how both these means of simplification can be applied simultaneously. An example is presented in which a typical combination of such issues are resolved for a system in which temperature control, differential pressure control, and the opening/closing speed of an airflow by-pass control vane are involved.