Star2Star VOIP - UTM Setup

Question

My question / dilemma may require several steps. I apologize in advance. 
 
 Star2Star is a VOIP provider in which it is somewhat proprietary / closed / locked down. I inherited it and must live with it for a while. They require their little "black box" have a Public IP address and sit at the edge of the network. I'd rather not have a switch in front of my UTM/s in order to "Split" the internet connection. They of course want their box in front with everything running through their box.. no thanks ... 
 So how do I make this work? 
 1. Physically - Can I just plug the box into any port on my SG210 and configure an interface and give it one of our Public Static IP's . 
 2. How do I let the connection to the Starbox be Open so it can communicate with Star2Star's systems ? 
 3. Internally all the phones must be on VLAN 41 (Tagged) to work. The Starbox hands out the DHCP address to the phones. How do I let this happen/ work ? 
 
 Let's start there.

BAlfson · Accepted Answer

I helped another Sophos reseller with this with a client of his last year and all traffic passed through the UTM and the *2* box was "behind" the UTM. One of the tricks we had to use was that one connection between the *2* and the UTM was an untagged VLAN connection. They have documentation explaining how to do this, but most (my impression) *2* installers don't know how to do what you want and will resist trying it. 
 Cheers - Bob