The frame issues developed under the fuel tank, near the cylinder head mount. They did indeed start leaking fuel when problems arose. It's easy to tell if you have an early '09 frame or a replacement by the placement of the gas cap. If the gas cap is centered in the middle of the frame (when on the bike, looking down at it), it's an updated frame. The old, older ones that had cracking issues had the gap offset to one side (left side, if I remember correctly). Keep your eyes on the bottom of the swingarm, where the linkage attaches.
Hard to tell on my phone screen, but I've seen plenty of aluminum welds on motorcycle frames that look like they are cracked on the edge, but aren't.