Never fired a Vang, and I try to keep an open mind, Bennett. But I wonder how much this is needed. I doubt it is ,tho it does sound right nice.And I'm NOT dumping on your or Vang.
For comparison, my HD, no choke 870 with the forcing cone job and firing my old duty load, Winchester standard 00,goes about 5-10" at 15 yards,20-24" at 25.Fitting that bbl with an IC choke tube and some judicious ammo choices should bring the groups down close to what you're getting.
As for the recoil reduction, this one comes in at 9 lbs or so. Kick's not a big problem.
And FYI, Remington Cyl bbls have a few points of constriction. Patterns get rounder even with just 2 or 3 points.