Believe it or not, wide-grip pull-ups/downs are not the key to lat development. All you need to do is combine an isolation exercise with a compound exercise. The reason is, during a compound exercise, the arms are going to be the weakest link, meaning, they will tire before you can fully stimulate the lats. Here is what I recommend, combine close reverse-grip (palms facing you) pull-downs with nautilus or dumb-bell pull-overs. Warm-up on the pulldowns first, maybe two sets. On the second set use a weight that you could do 10-12 times, but don't go to failure yet. Then do a warm-up set on your pull-overs, followed by a set to complete failure (ensure that you always use strict form), immediately go back to pull-downs, and do a set to complete failure, again using strict form. (I assure you that you will be lucky to get 6 this time) Building muscle is as much, if not more, about training smart, not just hard. If you are interested in a complete routine just email me. Good luck