I have two Novas. I put the recoil reducer in the tactical, which I bought for 3-gun shoots. I find it makes the gun more comfortable to shoot but can't estimate the % reduction in kick. It definitely improves the balance of the gun.......that's my bit for now.
I didn't install it yet in my 28" camo , which after a 100 clay sporting shoot, the shoulder is sore and bruised. Transfer from one to the other would be simple. I would also imagine that when you install it, it is critical to have the included hose ( which tensions the mercury tube in the bracket) cut so that it is snug when installed. I could be wrong, but that's the way I did it.
Mule