This can be done in any mode -- a regular game of Scrabble would probably be the easiest. You can do this by either creating a 7+ letter word vertically (up and down) or by adding on to other letters to make a 7 letter word. Using two controllers, you should be able to set yourself up to make big words. For example: "ER" is a valid word, so try to create that word vertically. Once you've done that, with the help of http://www.wineverygame.com you should be able to create a 7 letter word using at at least five or your tiles.