Do you have any pictures, I cant remember any issue with it. The bracket on my clyde smith airbox fits like it was born there, tho I did have to modify the airbox a bit to clear the accelerator pump.
I installed the original PA12 box from Clyde and don't remember an issue with the Bracket Air Filter but did have the same issue as Doug with the accelerator pump.
Doug, hard to see maybe with my pictures but where we’ve riveted some silicone we also bent the flange out a bit. As it was, that flange on the air box was metal against metal and fretting the filter assembly. There was also an 1/8” gap on either side that the silicone now seals.
The second photo shows the 1/4”+ gap at the aft end of the assembly. It could be the way the door is or some other defect, but the previous owner had just glued a piece of foam to the filter assembly to fill the gap (was almost coming off and threatening to be ingested)
We plan on fixing some more silicone on the back end to take up the space and we should be good to go.