That's not a problem on your side. The engine crops everything if you import it as an animation strip.
This isn't true.
I've just loaded 2 sprite sheets into the
animation. My 32x32 sprite sheet imports at 32x32 and my 64x64 sprite sheet imports at 64x64. No cropping on either of the 2 different sizes.
When I preview in browser the sprites size is 32x32 until it comes to the frame when the 64x64 sprite sheet starts and the sprite resizes correctly changes to 64x64.
So unless I miss understood your statement is complete rubbish.
Edit** Here's the sprite sheets I used