GTM- Private IP to Public IP Translation

I am trying to work through the same problem. As GTM is in DMZ running priv ip.

 

Should i define Vs with Priv IP or Define vs in Public ip on LTM?

 

 

GTM picks it up as its running on same box.

 

Then on GTM server put tranalation to Priv IP or public ip.

 

What i get from comments above is

 

define vs in public ip & when gtm picks ip vs in Gtm>servers then in tranaltion put priv ip.

 

If this is the case how can i allow all services or custom services to this server.