Depends on your definition of a RCD... Lol I'm not big on dogs going way out and catching on a big boar hog and getting cut down while we are trying to get to them. We hunt on foot, and our dogs are pretty rangy. If they were to go out .5-1.5 and catch we'd be screwed... Would probably walk up on dead dogs or a dead hog. We normally use these dogs for the stopping power. If a bay breaks out of a boar is walking on em, but won't stand, then we can wait until it sounds off again and send one in from 100-250 out. When we do let any of them go into catch we make sure we are right ur on their tails. They are more than capable of being RDCs, plenty of wind and leg, but just not how we roll if your explanation of a RDC is a CD that runs with your pack.
I guess what I'm saying is we'd rather conserve their energy so they don't expend it on one hog, that way they have the energy to catch more and keep making the long treks that we go on.
I will say with PJ that I've trained her to come back to me if she doesn't catch within 250 or so. If I see she's running and not caught yet, I can normally call her back and get her on a lead. But.... She is like the rest though, and if she sees the hog she's not going to stop. I've definitely had her get let go from 150, then go another 250 with the dogs and finally stop the boar.
So to finally answer your question, we pretty much use them as a lead in CD... But are comfortable letting them go from 100-250yrds to go in and put breaks on.
IMO this is just hunting intelligently. Seems most young doggers think you have to have a pack of alligators to catch a running hog, and although you can catch plenty that way, its only one way and IMO is not the best way bc of the time spent doctoring dogs, my loose bay dogs and dogos catch plenty too!