Using +20% happiness is a terrable waste of points. I would set it to 90% and place troops on all your planets. Use facilities such as the Urban Pacification Center (UPC) and or religious facilities if you take the trait.
Personally, using +20% for happiness is something that I would NEVER do. It is really a huge waste of points. My $0.02 worth.
For the best advise on Mini Maxing your characteristis you can read a great article by Fyron
LINK