Double click on the hatch pattern.  This should bring up the hatch edit dialog box.  Pick on Recreate Boundry, hit enter 3 times (read the command line so you will know whats happing). Now click on the hatch boundry and you'll notice you have pick boxes in the corners.  Stretch all you want.

You have created the boundry with lines.  When you do this you must pick the end of each of the lines, in other words pick both lines then pick the pick box at the end of the line, then stretch.  Hope this fixes your problem.