Make sure you repoint the animation if it's larger han the original (which it probably will be). Also, I'm way too lazy and unmotivated to find the pointer for FR, so mine only works for Ruby. I was able to edit both the Pokemon sprites (whose back and front animations are connected and thus the same) and also the backsprite. Actually all three character backsprites use different animations but I just set them all the same because it was easier, lol
By the way, I was using a different Edian than is used with Hex Editors (I was using a tile viewer after all), so try switching the values around a bit.
If this helps, you should be able to find it near the sprite tables.
By the way, this is Crazybuizel, if you didn't know already