The black LC-1 frames (used on all of the Hero packs) have the center bar flush with the rest of the frame. The green LC-2 frames, used on most of the GB2 semi-hero packs, have the bar slightly raised. Either way, you need to use some 1" steel spacers (or wooden blocks for GB1) to offset the motherboard from the frame.
They sell rubber spacers which may be easier on the cardboard and foam versus the metal or nylon ones. Maybe using those and not over tightening the screws will work?