Guys, never heard a bad thing about Vang, but....
Firing a standard 870 with a few addons shouldn't hurt. Like sex,if it hurts you're doing it wrong.Form,followed by stock fit, are the most likely culprits here.
My HD 870 with the mag extension, peep, SS, fender skirts and fuzzy dice weighs about 9 1/2 lbs. Duty load is either Federal or Winchester 00, 9 pellets. WHAT kick?
Technology cannot substitute for expertise.
IMO, you'd be better served with more ammo and range time. If you reach a plateau where only equipment upgrades can improve your effectiveness, Huzzah! At that point, you're truly dangerous, with or w/o the mods and addons.
This isn't a dump on Wilson, Vang, or thee. But it's been my experience that someone spending more on mods and addons than ammo and range fees needs to reprioritize.
BTW, I taught firearms to hundreds of Correctional Officers, and the only shotgun sports I've missed I know of is the European driven shoots...