Managed to figure it out... You need to create a BVI and put the IP for the subnet there. Then config encap dot1q under the gig port for the modules and specify the vlan number and then add those ports to the BVI.
For example... this will create 2 vlans (Data - 13 & VoIP - 18) that can be used across both switch modules:
!
bridge irb
!
!
interface GigabitEthernet1/0.13
description DATA
encapsulation dot1Q 13
bridge-group 13
!
interface GigabitEthernet1/0.18
description VOIP
encapsulation dot1Q 18
bridge-group 18
!
interface GigabitEthernet2/0.13
description DATA
encapsulation dot1Q 13
bridge-group 13
!
interface GigabitEthernet2/0.18
description VOIP
encapsulation dot1Q 18
bridge-group 18
!
interface BVI13
description DATA
ip address 10.10.13.1 255.255.255.0
!
interface BVI18
description VOIP
ip address 10.10.18.1 255.255.255.0
!