Pay attention to the weight you add and where you add it. The PTO is held in gear by a plunger/spring similar to what holds the transmission into each gear. If you put in a heavier lever, particularly with weight ahead of the current location, it may tend to disengage itself. It will be worse on rougher ground. Also keep in mind that the throw will get longer with a longer lever. A six- or seven-inch throw will require a lot of "reserved" space and may become a more annoying reach than reaching behind. You might consider making a lever that mounts at/near the front edge of the tool box with a push/pull link going back to the current lever.