The above jumper was made for my friends puppy using the pattern above but it ended up being quite short on her. It was a good tester though so we made her a new one so her little bum didn't freeze.
Its easy to just throw over their head and they are not restricted if they need to go to the toilet. Some designs go all the way under, which is just silly.
No pattern alterations other than to decorate it (as seen with my B for Busta hehe). I love it and I secretly think my pugs love it as well.