The Vigor 2850 offers 20 Port Redirection line entries. Some devices (NAS) can use pretty much all of those, leaving few available for other purposes. The Vigor 2760 now has 40 line entries. Any chance of upping the number on the 2850?

Whilst I don't disagree that 40 would be a more suitable number, why would NAS devices need so many ports? And are you sure it's such a great idea exposing them to the internet vs using a VPN?