This paper proposes a software design modelling approach that uses the Common Variability Language (CVL) to specify and resolve the variability of a software design, and the aspect-oriented modelling technique Reusable Aspect Models (RAM) to specify and then compose the detailed structural and behavioural design models corresponding to the chosen variants. This makes it possible to 1) exploit the advanced modularization capabilities of RAM to specify a complex, detailed design concern and its variants by means of a set of interdependent aspect models; 2) use CVL to provide an easy-to-use product-line interface for the design concern; 3) automatically generate a detailed design model for a chosen variant using a custom generic CVL derivation operator and the RAM weaver.