Nighthawk MR1100 - data offloading to a wifi HP printer extremelu slow

I have managed to get data offloading working. I have a HP Office Jet Printer 200 Mobile series  connected to the nighthawk printer, but it prints extremely slowly. For example, 1 page takes about 2 minutes to print. I have updated the firmware on the printer - no difference.

 

However, once data offloading is switched off, which causes a reboot of the Nighthawk box, the printing goes like a bat out of hell when the iMac is connected via 5Ghz and only slightly slower when connected on 2.4GHz.

 

I changed the gateway address on the Nighthawk to 172.168.1.1 so that it didn't clash with the gateway address on the box that we were data offloading to which is 192.168.1.0. Starting ip address on the nighthawk is 172.168.1.20 ending with 172.168.1.99

 

Any suggestions would be appreciated.