Hi,
and again a miscalculation by differing block sizes.
The adventurous proposal would be useless because working somewhere
in the still undamaged part of the image file.
skip= and seek= must be the numbers for blocks of 512 bytes rather than
of 64 KiB.
So this proposal should have been
dd if=/dev/sdd bs=512 skip=16500703 count=66 \
of=rock-img-shrunk.img seek=16500703
Have a nice day :)
Thomas