I had a day to myself so I attacked my piping problem. I removed the main riser from the bullhead T and relocated it over to the other main riser with a T. I know they should be on their own takeoffs, but for now that's the best I could do what with it being very cold out at the moment. At least now there is a modest header with a chance to drop the water. I also adjusted the pitch on that problem main to verify good drainage, and I reinstalled both my sets of main vents. So what did I get? I now see both sets of main vents venting in synch- both get hot and close at the same time- both sides of the house get warm at the same time. No gurgling at the radiators. Balance- woo hoo! Later, after heating season ends, I will build a nice dropped header. After looking at the G.W. Gill site jobs, I am inspired to do it right. Here are before and after pics.