Fresh air flap interference

[zambo]

I was just closing up my refurbed heater box and struck some interference from the rivets holding the new heater valve bracket to the heater box top. 
 

It appears they are preventing the fresh air flap opening more than a fraction of the typical travel. It’s hard to see the issue when the tops in place. 

There are a second set of holes in the bracket base which I will use to  rivet it to the top, after I drill the current ones out. 
 

My query is has anyone else struck this? I’m thinking that it seems strange there are optional pre-drilled holes in the bracket when it appears one set of them isn’t suitable anyway and would cause interference. Unless the innards of the heater changed over time, around the shape or size of the fresh air flap which meant the holes I’ve currently used would lead to interference ...?

 

[Son of Marty]

Try running the rivets with the head on the bottom that may give you clearance but it won't look nice

[zambo]

Good point. Not like anyone can actually see it.