what type of fuel tank are you using, i had this same problem with a WM tank, leaked half a tank of fuel through my fuse, but still flys today with a new fuel tank of course. a sullivan or du-bro tank would do nicly as they are top quality, try to get around the same size tank, i have used both and have had no problem .

the reason for your tank leaking may be because of the bung being stripped were the screw goes.