Some tanks need the increased flexibility. If you are nose down with less than half a tank of fuel, the standard fuel tubing may not allow the clunk to drop all the way to the nose of the tank. The air it picks up just doesn't burn and you get to practice dead-stickin' The dreaded stuck clunk is also fun. Once had a guy at our field spend three weekends trying to figure out why his engine stalled after 2 to 3 minutes of flying time. (Okay, it was me ) The clunk was stuck just about halfway up the from wall of the tank. I got awfully good at dead-stickin' that trainer. If standard fuel tubing will allow the clunk to travel the full range of your tank without sticking, it is fine to use it. Just rotate the assembled tank outside the plane and watch the clunk movement. Shake it around a bit to simulate plane movements to ensure it won't get stuck in actual use.