RE: usable fuel
if the point is getting all the fuel in your tank used up then go to a bladder tank, they cost a lot more. I have been flying models for over 30 years and haven’t had much worry with my planes cutting off in flight due to fuel starvation. most fuel lines are long enough and have fuel in them to keep an engine running when you are in a dive. I don’t run my tanks dry I know pretty much how long I can run on a tank of fuel depending on the model, but on occasion I do have a dead stick due to empty tank and when I remove any remaining fuel there is about half ounce left. if you have your fuel lines/tank set up properly it will siphon almost all of the fuel out. most of the maneuvers we do don’t last but a second or two. it happens but not a common thing at least not in my experience and not that much of a worry. I suppose if I were flying something like a jet or high end model I would make those assurances. but for sport flying or just putting around I don’t bother.