That works fine when leaving and you are only packing only your things and don't bring anything back that strategy will work but if you have packed other things that you didn't bring with you and you were close going down you could very well go over the limit. It is really hard to pack the exact same why you did when packing for multiple people as well.

It is also easy to pack exta things in you check luggage that was in your carry on luggage and without these scales you will not know what your luggage weighs when repacking.

Shak