Warning: This design sucks compared to my Longboi design. I did this before I had any exemplary modeling skill or software. It's also really hideous.
This pump grip works on both Longshot and Retaliator, and is the grip with the best functionality in existence. The reason I know I can say this is because I sacrificed all aesthetics for functionality. No other grip has. This grip is a beautifully functional, ugly-looking conglomerate of many different grip styles.
The model is scaled to 107% on all axes, so that gaps will form and fits are not overly tight, as 3D printing often ends up.
I use this grip on a 20kg LS, and it holds up fine and is very comfy.
2 pilot holes should be drilled in the slide on the top of the blaster, unless the brackets are fastened using an adhesive. Really quite simple.
The bipod legs have to be removed, and also the round protrusions they sat on have to be removed as well. A new bolt can be made from a threaded rod. Again, this is typical for pump grips.