it seems to work as well with just the waist straps... one has to lift it up to a higher spot in the center of the back sometimes, whereas the shoulder straps hold the support at the higher point all the time..and you can buy extra storage bags for it.. but end up spending more.. It's nice to have storage attached.
I'm rather small at 155lbs, but it seems like it has lots of adjustment in the straps.
My doc said I had to use one or quit shooting with my curved lower spine causing cramping in my hips and lower back. It has helped me stay out of cramps.
Ashland Air Rifle Range