Just to add some confirmation to this, I did this to a BR2001BL/SS which is the Edgestar unit sold as a KC2000 from kegerator.com. I figured I 'd give this a shot as after a while I decided I wanted a second faucet in my tower.
I bought a good quality hole saw, a Milwaukee Shockwave 7/8" from Home Depot. This hole saw has fine teeth for a smoother cut in thin materials.
I also had some of the black putty like stuff electricians use, duct seal, for the hole. I decided I didn't want to go big enough to fit a grommet.
I drilled approx 1.75" directly below the hole that was already in the unit.
Being paranoid, I started from the outside and used a small pilot bit. Once I was through the metal on the back I basically was able to push the bit in until I hit the back of the interior wall. Basically, the only thing there was insulation. I cut the hole with no problems, from the back as far as I could, then from inside the unit to finish it. Smoothed the hole down a bit and then ran my 2nd air line and my tower cooler power cord. I sealed the hole with the duct seal. I also sealed the OEM hose with duct seal as on my unit at least, it wasn't an air tight seal.
I had also asked this from Edgestar and they told me they wouldn't support the warranty on the unit. I could see if I cut into a refrigerant line, but that would be 100% on me and I wouldn't try to warrant the unit in any event. Then the Edgestar rep suggest I search the forums.....
Looking through their website, it looks like their two line unit is the same as the BR2001, just with the extra hole.
Hope this helps anyone contemplating this. As always, ymmv.