[DonRotolo]

Al said it well.
I would just add that having an extra inch or so for fingers to get at the batteries is valuable. If they rattle around, some closed-cell foam can be cut to take up the space yet leave flexibility for the future. (Foam that's soft but quite stiff, made of a slippery plastic I think is polyethelyene. Usually found in white, it is not styrofoam)