This paper extends the systematic model reduction approach of Robertson1, developed for startup/shutdown operations, to regulatory/servo control applications. The extensively modelled Fluid Catalytic Cracking Unit is used as an illustrative example. The ’Model IV’ FCCU model developed by McFarlane et al.,2 is transformed into a lumped parameter model (Tatrai et al.3) prior to linearisation and ’structure preserving’ model reduction. The performance of the reduced order model, used within a linear multivariable controller, was seen to lie within the pre-set bounds of the reference model. In contrast, the deficiency of traditional heuristic model reduction, is also illustrated.