I'm using Device Specific in one of my image sets (image0) and having 3 images for 2x, Retina 4 2x and 3x.
iPhone 6 Plus simulator uses the 3x and iPhone 4/4s uses the 2x.
The problem is that iPhone 5/5s simulator never uses the Retina 4 2x (green one in the screen shot below)
These are the resolutions: 2x: 640 x 960 Retina 4 2x: 640 x 1136 3x: 1242 x 2208
EDIT1
I tried as per the suggestion below to set the image in IB but it still selects the 2x version!