6mm Badger shows this configuration he did with the VFC AKS-74U GBB Rifle. He transforms his VFC AKS-74U into a modernized CQB powerhouse by installing a VFC adapter sourced from ProAct Store, allowing for a MIL-STD Picatinny interface. He then fits an ACETECH skeletonized MCX-style stock to the rear, ensuring the hinge is rotated to fold away from the charging handle for better ergonomics.

The Brain Exploder makes some custom products for airsoft guns using 3D Printing Technology and he has ready to be printed out and delivered to you is the Airsoft Shotgun Rail Adapter... "New addition to my Shapeways store is the Dual Rail Adapter that easily slides on and locks in place with no tools on to the popular and inexpensive spring powered airsoft shotguns by UTG, Bravo or Double Eagle.

Daphne of LCT Airsoft sent a link of a video showing installation of the LCT Airsoft PK-227 40mm Silencer Rail Adapter. This allows you to install rail mounted weapons accessories such as a tactical light or a foregrip. You can use two or three in combination to mount the accessories and you'll just need to adjust them to the left or right so that one accessory does not get in the way of the other. This will be available by the end of April 2014.