Tvheadend

I have a RPi2 running OSMC RC2 with TVHeadend as the backend connected to an HDHomeRun EXTEND that is being fed a ClearQAM signal from my internet/cable service provider. I'm in the US, by the way. I had to manually create the muxes as choosing the US-Cable-IRC predefined muxes did not populate any muxes to scan. After adding the muxes, i can veiw live TV, but the resolution is horrible. Interestingly enough, the aspect ratio is distorted as well. I was able to force the display of 4:3 video streams to 16:9 with the OSMC frontend client (PVR addon) (but i don't think i should have to do this). I have a Win7 PC running WMC with two AverMedia tuner cards, one of which is also connected (via an RF splitter) to the same signal from the internet/cable service provider. The same mux/channel displays with crisp resolution and in the correct aspect ratio on that system, so it's not the RF signal coming into the house. I suspect it is a tuner configuration issue.

I tuned the RPi (TVheadend) to a particular channel that i know is in HD. I then used a remote machine and hdhomerun_config (command line support tool for the HDHR devices) to query the tuner and found that the tuner was using a transcoding setting of "internet240", this out of the possibilities "heavy, mobile, internet540, internet 480, ..., internet240". So, the transcoding seems to be using a codec that highly compresses the stream, hence loosing resolution (this is my hypothesis).

So, the questions are:
1) does anyone know how to configure TVheadend so as to request a particular transcoding mode of the streaming source (the HDHR EXTEND in my case)?
2) is it even TVheadend that is responsible for requesting a particular transcode setting or is it the front end client?
3) does anyone have any useful information regarding my issue for which i've failed to ask a specific question?

I apologize if this has been previously addressed in another thread or wiki page. I'm at my wits end with this setup!