I actually started out at about 32 degrees, as I picked that as the rough center point of the two clusters in my area. Zero degrees turned out to do better though on avg for the major networks w/the 100k tranmitters. Plus the local PBS 30/15 seems to pull in better from the rear than from the side of the antenna. Probably has to do w/the trees around me - oaks, poplars, pines; all too tall to reasonably overcome. The rotor just doesn't make sense for recorded TV.
I did get an idea from Silicon Dust tech support. They suggested a 2nd antenna aimed at PBS 30/15, combined with a Jointenna. So on a whim I pointed the coat hanger antenna that's in the attic towards 30/15. I fed both antennas into a 2-1 and that went into the amp. From there it split 3 ways to the tuners. I expected the worst, figuring multipath and other issues. The result was a clear picture thru the HDHR for both of the PBS stations, 30 & 42. It used to break up every minute at least, but I watched for an hour w/o any breakup. The TV tuners are fine too and there doesn't seem to be any impact to any other channels.
This won't be my final setup tho, but for proof of concept, it works pretty well. I'll likely add a 2nd outdoor antenna, and possibly use the Jointenna or other signal combining device as needed.
As long as the HDHR is working, I'm happy!