Old Battery was so old and swollen that it was causing a crack in the back of the rear cover! had to be replaced.
The Battery that IFixIt shipped me was not tapped as tightly as the apple original one. it took a scary amount of pressure to get the battery in to place mostly is was the circuit board on the bottom of the battery under the orange tape that was sticking out farther then the original.
Amazingly these batteries seem to put up with a surprising amount of pressure with out seeming to take any functional damage. So if you have to cram one in just don't puncher it and it will probable be ok.