To add to the list of suppliers of BA nuts, bolts and washers, Hobby Mechanics (hobbymechanics.com.au) have a very large range.
Their range is larger than E J Winter, mentioned in earlier posts.
As another old fart engineer I would like to add by 2 bobs worth to the discussion. . I have now idea of Brian's experiences except he produces some damn fine models and his posts have helped me in the past. To the problem of fuel feed and raising the tank it sound to me to be about basic fluid...