Extract GIF frames retaining base canvas size + offsets

I am trying to extract GIF frames using ImageMagik convert command. The GIF images are optimized to only overlay animated changes (I believe they call it mipmap) and this is ideal for my extraction due to performance limitations. If I use -coalesce I lose the optimization since I'm using the GIF frames in a spritesheet so I need to extract it as is but when I do extract it with the standard convert xxx.gif xxx.png the animation frames are extracted without offsets and the canvas sizes are different to the base image (0).

I need all the images extracted to match the first frame with retained offsets from the GIF meta-data. I have no idea how to accomplish this in ImageMagik and want to know if this is possible?

Then if I get them matching sizes with offsets applied I can add them to the sprite sheet easily.

Would appreciate all the help I can get! Thanks.