First let me say that I would never want to be a participant in an Edgar Allan Poe story, specifically "The Fall of the House of Usher." While I can respect Poe's works as timeless horror stories that are well known and frequently analyzed, I can also recognize that his style is not my particular cup of tea. I don't watch scary movies, I hated telling ghost stories around the campfire, and on halloween I am always the friend dressed as a fairy or a bunny amongst the mummies and zombies. Let me put it this way: Nancy Drew books gave me nightmares when I was 11 years old. But after reading Poe, Miss Drew wasn't looking half bad.
So it's pretty clear that I am a HUGE fan of happy endings. If I was forced to be a participant in "Usher," my first hope would be that the ending would be happy. However, I feel a happy ending to a story like "Usher" would completely demolish the fearsome quality the story possesses. So out of respect, I would not change the ending.
After much thought about preserving a good horror story I have decided that I would change where Madeleine was buried. I think that if Roderick and the narrator had buried her in a place that was inescapable in the first place then there would have been no chance of Madeleine later reappearing. Instead of both the Usher twins dying, only Madeleine would have been guaranteed dead (and let's be honest, she had one foot in the coffin from the beginning). The worst part of the story for me by far was when Madeleine reappeared to Roderick and the Narrator. My alteration would eliminate this part, thus saving me from days of nightmares.
Fortunately I am not and never will be a participant in this frightful tale. Unfortunately I will never be able to forget the image that appeared in my head when I read the ending of "Usher." I hope you're happy Poe.