Fishing rivers, weight is determined by the current for me. I want to control what the tube does, not the current. If the tube is tumbling downstream out of my control, I need to go heavier, but just enough so I make it move, but not so heavy that it becomes an anchor. The fall is not that important to me. If the weight is right, you can feel everything that tube comes in contact with and you'll get a feel for just what that is; wood, rock, sand, mud, grass. More often than not, the bite is suttle, the smallie just picks it up or just a little tap. You'll learn that feel but only if you can stay in contact with the tube with just enough weight. Most of the time, 1/4oz for me, less current I can get away with 1/8oz, especially with the 2.5" tube.