On my 09 V, I have the Hyperpro 460 with a remote rebound adjuster and built for a 30mm lower seat height. It also has high and low-speed compression damping adjustments. My riding is mostly on paved back-roads. The shock gives a very comfortable ride, much better than the OEM shock.
Earlier I had only the Hyperpro 30mm-lowering progressive spring on the OEM shock, which made a nice improvement in ride comfort. For my riding, the Hyperpro progressive spring alone gives almost as comfortable a ride as the Hyperpro 460 shock.
My OEM shock rebound adjustment screw turns easily. I suspect your screw may be corroded.
I also use Hyperpro 30mm-lowering springs in my front forks. All the Hyperpro springs (and the 460 rear shock) worked as advertized, and made a nice improvement in ride.