This is pic of my v band slid over the end of my collector.. Notice the gap!! Its only that bad on one side.... Sticking a pipe expander in the end of the collector would most likely cure this but may explain the leaking issue..... Especially if y pipe expansions are as out of round as my collectors are.... Be willing to bet if youd run a pipe expander in both sides of the slip joints, you wouldnt be dealing with leaks....