An arrangement for mounting and supporting a plurality of cylindrical form or other computer systems, for example Apple Mac Pro cylindrical form computer systems, in a data center so as to optimize cooling air flow, access to cabling, and maximized use of space. A plurality of shelf assemblies is mounted to a computer center rack. Each shelf assembly comprises a tray that supports a pair of slidable sleds. Each sled supports a cylindrical form computer enclosure in an axially horizontal configuration, and includes a sled face that exposes a top surface of a computer enclosure. Air flow perforations in the sled face direct air into the space behind the sled face and across a mounted computer enclosure. The tray and sled provides a convenient arrangement for power and communications cabling, as well as directs a cooling air flow through openings in the trays and sleds upwardly across computer enclosures.