We have used direct burial cat 5 before. It will last for many years with no problems. Cost's more though. Be careful on the crimped ends. In my experience they are the cause of many problems. If you feel like it, just put cat5 jacks on and use store bought patch cords. As far as the 300' limit, in school they said it is mostly to prevent timing problems with the data and network collisions. That being said, I have installed 350' runs that work fine. I would assume your plan will work, the only thing I would do different is use direct burial and jacks with manufactured patch cords. Keep those twists in the cable when terminating, very important. I would also use some pipe on either end when coming up out of the ground, prevents weed whacker fade issues.
Last edited by stevemc; 11-15-2012 at 04:55..