How do you know that the Nighthawk is restricting bandwidth? Can you turn off any QoS or bandwidth control settings?
Otherwise, the only way I think you can solve this problem is by enabling port forwarding for the Nighthawk’s IP address on the modem, if this feature is supported. This is very risky because you’re essentially creating a hole in the modem’s firewall to allow ISP traffic through to your local network. And if you don’t have a static IP address for the Nighthawk, then *anyone* assigned to that IP address on your ISP’s network can connect to the Nuprime.