Extreme Gear Labs shared these photos on their Facebook Page. They show a Haley Strategic Partners D3 Chest Rig attached to the compression straps of a 3 day style backpack to serve as a compression panel. This is a handy trick that should work with a number of different chest rigs and a number of different packs as long as the buckles match. In this configuration, the user can use the chest rig to stow compressible items like outerwear.
Eggroll is a pretty clever dude.