So I did a search on "stairs" for you, because I'm nice and I've been having some stairs problems of my own (I hardly ever use regular stairs: I love me some modulars, though). I always have to knock out a wall or use moveobjects on to get modular stairs where I want them these days. Also, the amount of space that stairs take has increased by a tile, which is annoying. I used to put a fence railing around the stairs at the top, and it only took three tiles, the same as the length of the hole in the floor. Now I have to leave a five or six tile hole in order to get modulat stairs to place, though I can fill in all but the three tiles after: but a railing has to enclose four tiles. Annoying, but liveable.
...
...
I don't remember where I learned this trick, but I have used it since installing all the EPs, including M&G, so it should work for you. Have the moveobjects on cheat active, remove as many floor tiles as needed, place the stairs, save the game. Move the stairs outside somewhere, close up all but 3 of the floor spaces and place any railings around them, then move the stairs back in. You can also place walls at this time if they were giving you a problem with the stairs in place.
SK