Right now, the run of coax is way too long, but I am going to cut a hole in the outside wall of the garage above the sliding door and epoxy in a big piece of PVC to use as a pass-through (Scarlet will just love how that looks!) to make the coax runs as short as possible. I bought a long enough piece of the LMR coax so that hopefully I can get two runs up the tower out of it and use the other piece for the 420 MHz receive side. That should hopefully improve my reception side a little bit as well.
But at least now getting into the ATV repeater is no longer extraordinary.