I have the adhesive catheter/overboard system. It works great. The tube exits the fuselage bottom a bit off center. I just put a little rudder in to yaw the ship when necessary. This seems to keep the stream of the bottom. Pour some water through at the end of the day to keep things clean. One consideration is the temperature. You don't want the tube clogged with a frozen block of urine. My solution is a second length of tubing with a quick disconnect. When finished dumping ballast I disconnect the catheter, connect the second tube and blow air through and then re-connect the catheter. I've heard of a t-connector being used for the same purpose. As mentioned in another thread, there seem to be two types of catheters - those that won't stay on and those that won't come off. The second is better. There is a liquid called Detachol that releases the adhesive pretty much instantly. Goo Gone might do the same thing but Detachol is made specifically for this purpose. Check the archives, this topic has been discussed thoroughly in other threads.