If you don't mind a more generic approach, check out "Challenge of Champions IV" in Dungeon #91 (hitting the shelves right about now). It's a series of ten puzzle-based scenarios, suitable for PCs of any level. On the plus side, it would be a simple matter to incorporate into your campaign: The PCs' rivals learn that the Adventurers Guild is sponsoring the latest Challenge in a nearby city within a couple of days and challenges the PCs to enter and try to achieve a better score than their own team does. On the down side, the ten scenarios are not geared toward specific character classes, so there's no real "ranger vs. ranger" event or anything going on; it's all "team vs. team." And, unfortunately, the Challenges of Champions are built specifically for four-person teams. Of course, you can always split your 6-person PC group into two four-person teams and have both teams compete. (The adventure includes extra NPCs to round out a given team if they're short a team member or two.) Just a thought.