I have had one for 3 years? I really like it and have tried it in various configurations. I use it for ligth weight gun. It is on an old wingmaster receiver with a standard mag tube and an 18" barrel. This past deer season I tossed on my rifled slug barrel and used it with the same gun.
I was laying prone in the dirt for one shot and it never even bruised the top of my shoulder.
Regardless of barrel length, I like having a compact light weight gun that is easy to drag in and out of the truck. Also takes up less space in the tuck or tent.
The real test was about a year ago at Thanksgiving. I went to a friends house and we did some shotgun shooting. All kinds of "targets" etc....there were 3 or 4 teenage boys there and everyone of them liked the gun. They liked all the guns, but they all enjoyed the knoxx stock a lot. These were not accomplished shooters, but by the end of the day they were hitting clays with all the guns, even the Knoxx.