Why a 1950s light carrier could reuse Colossus dimensions

Why could a 1950s light carrier proposal retain Colossus-class dimensions?

More compact machinery and a proven in-service design reduced weight and development risk.

Postwar machinery could deliver the required power from a smaller and lighter installation than its wartime predecessor. That saving created room for modern equipment without forcing the ship far beyond Colossus-class dimensions. Continuing a design already in service also reduced technical and construction risk. The proposal therefore combined improved machinery with the institutional value of a familiar carrier hull.