Stephie,
Unfortunately, with only the 2 Quintums you have, you cannot share the IP address between them. Each Quintum must have its own Public, IP address. The only way around this is if you were to setup a NAT with private IPs to the Quintums, but you would need to purchase a Quintum Call Relay to translate the one public IP to each of the 2 private IPs of the Tenors.
Mike