I have been dealing with some SI issues. I found that Jill Millers Alpha Ball was very helpful. It is not as aggressive as a lax ball or even the supernova or novito. I use the glute smash and floss, the high glute, and the QL mobilizations pretty much everyday. Also if you are tight in the front of the hip that could cause SI joint pain. So couch stretch often especially after long bouts of sitting. Jill Millers book The Role Model also has an awesome low back sequence that I found very effective as well. Hope that can help you out a bit.