Hi all, I think I got sorted on this now. I've got a remote office with 5 public IP's, 1 of which I want to be general NAT address, one of which I want to be fully open (DMZ) for a dedicated VC unit. After a bit of reading I've configured:

WAN IP Alias (added the VC external IP address), unchecked the join NAT IP Pool for this additional address
Added DMZ host to WAN2 with above IP external address, mapped to the correct private IP
Opened all ports TCP+UDP 1-65535 on that same aux address so that local IP Address (bit weird as IME DMZ should infer that, but I guess DrayTek is going the belt & braces route)

VC seems to work fine (at least now :lol: ). Anything I have omitted?

Cheers,
Jon