UPDATED(2019/09/01): See below.
Liked the original, but I needed an alternate version.
The original appears to be designed for much thicker cords and narrower chest. Modified the shape and design to suit my two cord backpacks at three different widths that maintain the size of the cord holding section to offer flexibility. These also appear to be tight enough to ensure the cords don't slide around too much.
UPDATED(2019/09/01): Added 150mm length one for people with broader chest or like the bag to hang a little lower.
I didn't bother using Customizer. I just chopped up the original until it had the design and shape to fit my needs. Did this all in "3D Builder" on windows.