sprites changing size question

So I have two sets of sprites that I'm working with. One is the walking and the other is the attack.
My character walks fine at the size I want, but as soon as it switches to the attack animation, it shrinks.
This is because my frame size for the sprites for the walking and attack are different sizes.
So, instead of making every frame the same size, I wondered if there was an easier way to keep a consistent size of my frames in GameSalad?
Any help appreciated
thanks