That certainly works. The triple task list is not really a GTD concept as it involves priority. Fro me however it works to think in terms of limiting my focus to three tasks at a time. I try to spend as much time with this list during the day and find it makes me very productive. I use as many categories as needed in the capture section. I find the 80/20 is simply in using it, as I know all I need to think about is in there. Further subdivisions does not add all that much for me compared to just having it all captured in one place.