The 4800G switches can support up to nine switches in a stack, using XRN feature in the later version. Take a look on the datasheet specifications (Page 6):
----------------------------STACKING-----------------------------------
Use optional CX4 or XFP connections for high-bandwidth stacking of
multiple units
Resilient stacking; full duplex bandwidth of 96 Gbps when using CX4
cables and link aggregation (48 Gbps without aggregation); 40 Gbps when
using 10-Gigabit connections
Single iP address and management interfaces for stack-wide control
hot-swappable, closed-loop resilient stacking
Distributed Resilient Routing with router tables in all units; no
master/slave arrangement
Combine any Switch 4800G models into a single stack, up to 9-high, when
using XRn technology
------------------------------------------------------------------------------