I know someone sealed above their rear left window and that worked for them.
Start from low and work to the higher points. That way if it's leaking from a lower point, you'll know instead of pouring it on top and the water draining down tricks you into thinking its up top.
I've eliminated all of my leaks except for the one that is under that rubber trim along the sides of the roof. I just need to know how to take them off, or at least seal under it.