Documention is very limited, but my setup works well enough, I'll keep this brief. :)
Anyone else reading this spots something wrong, please point it out.
Anyway, i'm running Build: 4.1-986~gfb9044c of TVheadend.
The cables also have to be plugged in order on the netstream, there is a primary lnb connector.
In TVheadend, under tabs configuration\General\SAT>IP Server once the netstream has been auto detected.
You need to set the RTSP Port as the netstream, mine is 554.
Under Exported tuners, by default there all 0. I'm only using two tuners on netstream (two cables from the LNB). So under DVB-S2 mine is set to 2.
Then under Configuration\DVB Inputs\Networks, then add a new network, "DVB-S network". not IPTV.
Set the normal, Name, Pre-defined muxes and Orbital Position etc.
Under Configuration\DVB Inputs\TV adapters, Enable the tuners in use only and set master tuner as required.
Under Position #1 (AA), I've only enabled this one, as i'm not sure what Position #1 #2 #3 #4 really does at the moment.
Set the Network you've created under Position.
The rest of the config is normal tvheadend stuff.