I have got an idea. Why don't you make the castle with multiple floors (for example 3 floors) and put checkpoint at each floor and on the third floor you put a checkpoint and then after putting some obstacles then mario should come down to the second floor. Then make some obstacles on the second floor. Then mario will come down to first floor. Like this, take mario to ground floor and then put a warp to the second section and there you can put your final browser with peach. How is my idea?