I have used alot of them, both in training, and in a work enviroment. They can be effective to stop an aggressive action, BUT I would not trust them against an armed perp. The Defense Technology 23HV, and others, are considered lethel at ranged under 10 feet, and I have seen them penetrate skin at ranges of 20-30 feet. That being said, I also know of one inmate that was shot over 40 times while he was beating the he11 out of another inmate, and would not stop fighting.
On the other hand, some DOC strike force use single .75cal rubber ball rounds in the shotgun when lethel force is called for in a cell block. It is reasonably accurate at ranges occured in a prison, and lethal. To be considered less lethel at close range, they have to be skip-fired.
Would I use a rubber shot type round for SD? HE11 NO. If it was my ONLY choice, I would go with either the single round ball, or the fin-stabilized "baton" round.
Sparky