2 BID added to spread load to 2 hinges. Side note to Conventional taildragger (could have been a Mono) that came to Rough River 2007, your lower hinge area was cracking, you left before we had a chance to tell you.
Another note is when strengthening lower 2 hinge areas, because of 2 BID on the inboard side of flange and a piece of 1/16" thick G-10, rudder is offset outboard by about 1/8" which will cut bout half of fill needed on starboard side to somewhat match vertical fin. 1/8" thick G-10 spacing was needed under middle and top hinge to match hinge line.
Y9-04-05