How do I print a 5 X 7 print on Pixma MG2520?

My new Pixma MG2520 makes great prints, but for the life of me I cannot get it to print a 5X7 Print.  It will print on on 5X7 paper but no matter what I have done including trying it on two different computers, it leaves large unequal borders.  I have tried printing using the Canon software and Photoshop and Lightroom.  When it shows the print in the preview it shows that an area of the paper is blocked off.  It shows me what it is going to do, but I can't get it to change.  I tell the computer that I'm using 5X7 photo paper, I use a photo that has been formatted to 5X7 (and some that are not) I've selected the option to size it to the paper size, etc. etc. etc.  I'm using up a lot of the ink trying different things to get it to print a 5X7 print with or without borders.  The final print comes out at about 4.2" X 6.2".  It does not center the photo.  The photo shows the blocked off area and it does print just as it shows.  I would love to know how to fix this.