I never have noticed any streaking or signs of fuel coming out the vent.. Think about this- when the vent trys to become a drain, then there is no vent to let it, hehe... If you notice in the pic, I have a loop in the vent tube for that reason (which may work better if it looped to the bottom of fuse, then went to top), but I would also assume that the flow of air into the vent also helps keep fuel from exiting vent when inverted.. Many guys do put the vents out the bottom, but I chose the top for several reasons ,similar to kevin #1- keeps belly slick and less possible damage in case of a belly landing , #2- not as much chance of fuel spills from residual fuel during transport, #3- less fuel on your hands, especially when removing taxi tank line just before take off, and #4- easy access is probably the biggest reason, not having to bend my wore out body over or kneel as much to attach or remove the taxi tank line... One interesting thing about a lot of r/c plane kits is lack of precise instructions on how to set up the equipment,. partly due to the many variables of engines types, tanks sizes, landing gear, etc and the placements of them.. This being my 1st turbine jet, I did a huge amount of research on it before building. There were many possible ways of doing everything to be done.. I took what I had seen others do and used the ideas that I liked best. Some things were my ideas, but not many..