I think you got nailed down like it is, I´ve been reading the pro.astronomer page Starheads and thats how I understand it works.
The slingshot effect (witch Nasa is thinking of using in the future for space travel) is the main element that keeps and maintains the steady orbit of the AA29, much like the earth´s and the sun´s relationship. Garvity + Mass + linear momentum.. and all that jazz :-)