Intercepting pan gestures over a UIScrollView breaks scrolling

OK, I figured it out. I needed to do 2 things to make this work:

1) Attach my own pan recognizer to the scroll view itself, not to another view on top of it.

2) This UIGestureRecognizerDelegate method prevents the goofy behavior that happens when both the default scrollview and my own one are invoked simultaneously.

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return YES;
}