Custom IP Address

ssh into the mod, then mount the FS as read-write:

mount / -o remount,rw

then run:

sed -i "s|192.168.51.1|192.168.51.2|" /etc/network/interfaces /etc/ssh/sshd_config
sync && mount / -o remount,ro && reboot

NOTE: At this point it's not possible to have 2 MODs connected via USB, even if they use different IPs.
If you need 2 MODs, consider using one MOD connected via USB and the other connected via Bluetooth.