Is the pic above from the actual stereo? If so it looks like the two left most RCA jacks are F C in and R C in? Presumably front camera in and rear camera in.
Edit: Literally didn't even read your post.... I concur!
I got really stuck with my Pioneer when installing the camera, I eventually RTFM and realised it didn't go in the yellow video input, there was a brown one for reverse cameras.