I cannot manage PacketShaper via an ISL trunk, but I am able to manage the backup PacketShaper (which is not on an ISL trunk).
It is not possible to manage PacketShaper via an ISL trunk. You cannot gain remote administrative access. The PacketShaper network management interface cannot recognize the 802.1q packet format. You can either use a native VLAN which does not tag packets or use a LEM card to manage PacketShaper. Connect the Inside LEM port to a spare switch port on VLAN1. Assign the unit an IP address from VLAN1 subnet.