Tvheadend

Hi there, first time poster, new TVH user.
I'm using TVHeadend running on an Openelec XBMC box, with an HDHomerun Prime 3-tuner box. I'm not using the CableCard feature of the Prime though, just trying to get all my ClearQAM channels visible.
I've gone through the TVH basic config steps, added DVB Network by location, Mapped DVB services to channels. I initially chose "us_Cable_Standard_center_frequencies_QAM256" as the DVB network to add. This resulted in 158 muxes found. I then mapped the DVB services to channels (I had already created an xmltv.xml file using http://mc2xml.hosterbox.net/ and placed it in the appropriate folder on the xbmc machine.) After this process was finished, I went into the Services tab, and there I see 158 services, but only about 10 or so of them had a channel name and a service name. The rest of the services had no service name, and the channel name was "_Unmapped_." Of the ten or so services that actually mapped, only a few of them were TV channels of interest to me.

So, to my question: how do I map the rest of these services? The service name is blank, and the channel name is unmapped. I've seen some How-to's that say you can manually add the channel name in the unmapped cell, but I don't know which service is which channel. If there's nothing I can do with these, is there another way I can find and add the rest of my local TV channels that I want?

FYI: The HDHomerun works fine on Windows Media Center, and I'm pretty sure I've got the XBMC side of things working pretty well, as I can view the 10 channels in XBMC Live-TV fine. I just don't have the rest of my local channels available.

Thanks for any tips, pointers, help, advice... etc.!
KC