In this paper, we share our experience of developing a hybrid execution environment for computer-interpretable guidelines (CIGs) in PROforma. The proposed environment is part of the CAPABLE system which provides coaching for cancer patients and decision support for physicians. It extends a standard PROforma execution engine - Deontics Engine (DE) - with additional components that act as wrappers around DE, allow handling of non-standard tasks, and facilitate integration with the rest of the CAPABLE system. This yields a hybrid environment in which the standard engine and specialized components must be interfaced together by some intervening layer. In the CAPABLE system this has been achieved by defining a set of specialized meta-properties which are attached to data and tasks in the PROforma CIGs to specify the interface between engine and components.