I actually cut my front frame while it was still tacked on and remade it on a jig with "brackets" mocked up.
http://locost.lt/download/file.php?id=53
In the end it did not help. Probably due to the height of brackets being 1-2 mm out of spec. My jig was just two pieces of MDF with carefully measured and drilled holes. Worked quite well:
http://locost.lt/download/file.php?id=138