[ww520]

And/or heat up the air filling the bag. As air cools, the volume decreases.

The right solution would be to squeeze to depress the bag a bit as it's sealed. Increasing the seal strength is a quick and dirty hack, but as we've all learned too well from software, the right solutions often got trumped by quick and dirty hacks. The customers just have to live with the consequence.

[jbri]

Your ideas have other suboptimal consequences though - sucked-in bags don't look as nice on the shelf, and in fact they look smaller. This makes them less attractive and thus less likely to be purchased.