I have a notion called the Bobbin Genie. It is a little silicon disc that goes in your bobbin and keeps you from getting bird nests. Here is a link to a UTube video on it. Also one source where they are available.
http://www.youtube.com/watch?v=Hdo_q0M2rsw
http://www.clotilde.com/list.html?criteria=bobbin+genie
Another notion I read about that many long arm quilters use in the Towa bobbin case tension gauge. Maybe either of these can help with your tension problem.
http://columbiariverquilting.com/tow...ion_guage.html