I wondered about some kind of prioritisation but it shouldn't be interfering with packets in bridge mode, that's the router's job. I already did what you suggested and tried running ping tests from the inside to the net, with mtr and a PC utility I found, the results didn't look obviously bad but I probably need to find something that produces reasonable graphs if I want to explore further. Anyway I'm back to the HG612 now so I can monitor my connection somewhat better.