heres another mod to give your spring shotgun a book of eli type look. I did this with my double eagle tri shot shotgun with a full stock, I'm not sure how well it will work for other shotguns.
Step1: remove the rubber butt plate exposing a screw
Step2: unscrew and remove the screw, then the stock should just slide off
Step3: remove the stock, where the stock used to be there should be a 2 or 3 inch tube that sticks out the back
Step4: cut a 3/4 inch dowel to the length you want and hhold it to the tube at the angle you want.
Step5: cover the dowel and tube with duct tape (I used gorilla tape, it's thicker and stronger) be methodical, don't just throw on tape willy-nilly. I started where the tube met the dowel and then worked my way up and down several times in a single long strip until the tape was flush with the rest of the gun the new handle was a comfortable size.
Step6: add one or two layers of grip tape to for comfort (you can layer the tape to make the handle shaped more realistically)
if you have anymore questions ask me and i'll try to clarify
Outdoor Primary: CA SLR105 tactical
CQB Primary: Echo 1 G36c
Main Secondary: custom sawed-off DE shotgun
Current Sidearm: Echo 1 Timberwolf
Specialty Weapon: Iron Airsoft M320 grenade launcher