I know exactly what you are going through, I had a way different design in my head before my mountain was done. My problem was to drop the track one foot at a 4% grade. That is about 25 feet of track on a small table with a 48 inch curve..
I also had a much longer tunnel to start with, then my wife said "who is going to see the train in a tunnel?" A good point so I made it way shorter... Maybe you need to talk to your wife? :-)
