Hello Bj?rn,
I am surprised at your 1.7 Mbit as that is the traffic I get from the remote to my HL2. From remote to ctl-head my traffic is 212 kiB/s on receive and 198.7 KiBs on transmit. This is easily run over an internet connection and not too hungry when using a mobile phone as a hotspot. Having said that I am very interested in how a divide by 4 would go and 12 KHz would be a more useful audio bandwidth as it gives some measure of fidelity when listening to broadcast band music. FreeDV codecs are another possibility and although there is a fair bit of unnatural sound to the voice it is perfectly good communications quality and we are looking at sub 2 KHz bandwidths here.
73, Graeme ZL2APV