Ok, this is how I convinced myself to keep airbox.
Since we have 2 separate engines turning one propeller, we need to make sure that same amount fuel/air mixture is going to left and right side.
We do carb balancing and using balancing tube for that reason. So, make sense to create situation were this 2 carburetors pooling air from same box with only one air filter that installed exactly in the middle.
So, airbox will stay. Thank you.