If you are missing the precise areas you want, I'd suggest that there are more precise methods of defining a download available today.
http://www.backcountrynavigator.com/content/view/79/46/You can use the placefinder to add several places of interest and then define rectangles to get a better area defined.
Even better, you could download detail level at 64m or 16m for a much larger region. The lower res may not be much use for you in hiking, but they may be detailed so that you can mark more rectangles and get the actual area you want.
The desktop version will complete downloads faster and a cradled download will be faster (and less costly) than wifi or phone service.
Nathan