No, changing geometry doesn't risk any data.
But if you'd like to change geometry, there should be a reason for.
Mostly, just required if partitions overlap and you can't recover it because two partitions can't use the same space or a partition is not found.
Changing geometry has no influence on cloning disk, if you have bad sectors.
Did you already try testdisk / advanced and ImageCreation?
Some info;
http://www.cgsecurity.org/wiki/Media_Image
Fiona