To date, Imaging Atmospheric Cherenkov Telescopes (IACTs) have primarily been realized using photomultiplier tubes (PMTs) as light detectors. Recently, such telescopes of small size (∼4m) have been built using silicon photomultiplier (SiPM) sensors in their imaging cameras. This work describes a design approach for SiPM based focal plane experimental instrumentation for operation alongside the PMT based camera of a large IACT. The initial information gathered during design and operation of a first prototype single module installed alongside the PMT camera is summarized. This experience has been used to design two new alternative modules currently being implemented.
