I simply use the Crop tool set it to he high/width you desire and drag i over the image until you are happy with what you get. Also gives you the option to set the resolution and black out the unselected area so you can see what your working area will be with out the distraction of the rest of the image. It is also possible to resize the crop selection with out starting over. This is the method I use to size all my work and I have not had an issue printing as large as 16x24