Sorry for chiming in so late. All you have to do is running ddrescue as described in the article. You do not have to adjust the size of your disks in any way. Once cloning finishes, it will say
and that’s what we’re waiting for. After that, you should be able to boot up, as usual. If it does not work, all you have to do is purging and entirely reinstalling GRUB2, that’s it.