No, not a bird, or the Rev Awdry’s pannier tank, watch your head!
As an inveterate bodger I always use the simplest possible way of doing things and the simplest way of making sure a model railway tunnel has sufficient clearance is to build it around the biggest locos that will pass through it. In the case of the FCPyF that means the Peru Rail diesel and GE Shovelnose #29.
The new module might look a mess at the moment but it will soon start taking shape once the substructure, or “geology”, has been completed. That’s when one of my favourite aspects of the hobby will come into play – making mountainous scenery.
As a child I was dragged all over Snowdonia and the Lake District by outdoor type parents. As an adult I think mountains look better from the bottom and there’s no point climbing them, better still just make models of them in the garage and there’s no need to get wet by standing in the rain to admire the scenery.