To achieve an objective designers often need to make trade-offs between multiple parameters. In incremental design or during the design process an additional objective is often to minimise the changes they need to make to meet the objective. This is in particular an issue for systems with product platforms, over individual components are over-designed. This paper argues that designers can think about this problem in terms of the margins on the objective parameters as well as the parameters that are traded-off. This is illustrated with the case study of an engineering cooling system
