Thanks to all who responded.
No Static: That's a good idea. I tried moving the antenna around a little when I installed it, but only so far as the existing coax cable reached. I have the antenna positions as high as I can in the attic, facing through the wall (the spot where it aims 60 degrees is one of the few spots where its aimed through a wall and not through either the roof or a neighboring townhouse). I can easily run a fresh cable through the attic opening that's long enough to allow me to experiment better.
GroundUrMast: Thanks for the recommendation of the Antennacraft HBU-44 or HBU-55. Those are long antenna (116" & 145", respectively). I'll measure next time I'm in the attic to see if it will fit. I think it will, if I mount it must above the ceiling of the room below. [Need to think - not sure if I'd rather try the larger antenna in the attic first, or try the C2-V-CJM on the roof first.]