When converting some VCD's to DVD I usually crop them a bit if they look like 2.35:1. I'm trying to get them closer to FS which my family screams for. These are basically throwaways.

Usually a value of 30 all around seems to do the trick. My question is should the L/R value be different from the Top/Bottom value to maintain proper AR?

If I use a 10% factor I get values of 24 (10% of 480 divided by 2) and 36 (10% of 720 divided by 2). Would the T/B then be 24 and the L/R then be 36? Am I thinking clearly on this?