Hi Michael. The Device Manager does not support the 4500G stacking feature; you can manage the stack through the web console only.
The config guide is poor when explaining the stack feature implementation, and you need to perform some actions beyond the commands you already have entered.
The 4500G stack is a "cluster like" stack, with one master switch and slave switches. Through the master you will have access to the others, using the command "stack switch-id to <id_of_the_slave>". The stack does not work as a single entity, as in the 5500G-EI and 4800G stack feature.
The additional actions are:
In the VLAN interface 1 on the master switch, assign an IP address of any class you want. The slave switches will obtain IP addresses by DHCP from the master, after you finish the settings. You can define the IP addresses in the slaves if you prefer.
In the stack ports, you need to setup the ports as trunk ports, with all VLANs allowed, and using the PVID of a VLAN interface that you are using in the local network. I suggest to use different VLANs than the VLAN 1. Use RSTP in all ports.
Note that the slave switches does not maintain always the same ID, when rebooting the slave switches or all the stack, the first slave switch that came up will receive the first free ID of the stack, and so on.
The advantages in this feature is the faster convergence and the bandwidth in the switches connections (10G), but even simple features as distributed link-aggregation does not work in this kind of stack.
HTH.