I did a mockup of a idea for the concept chest.

and I did a size comparison for a backpack, the templates used is the bazookajoe.
the left is a HS backpack, the right is a 75% scale of the joe pack. I am thinking I need to upscale it a bit, I think around 85%.
I am wanting it to fit between the shoulder blades, the HS pack is close to covering half of each blade.

Just added new compare pic, the red/pink is at 85%

Comments please??