Agreed I was going to offer that suggestion as well, but opted not to. When Viewing a map on the Map Tab, there is a Zoom tool button for selection. This allows you to Rubber band around the desired area and will give you that exact Zoom View. If I want the map to fill the screen to exact proportion, I make sure to get as close to the map in upper left hand corner and drag to lower right hand corner as close as possible to map and then left go. Just remember to go back to the Pointer or Select tool right away, otherwise if you forget then when clicking into the mapping screen will affect the view you currently have. I actually use this tool all the time and has given me the zoom results I was looking for. Hope this helps!