Where did u cut the hole for your mailbox mod???

Im getting ready to do the mailbox mod on my masterbuilt 2 door. Ive got the amnps, but not sure where to cut the hole for the flex pipe???? On top makes sence, but would be easier to seal if i put it on the side or back of the mailbox as the top is rounded opposed to flat. Guess i could put it on the side and lay the box on it side making it on top...

Also did anyone add additional draft holes to the mailbox???