Oh, and BTW, I pull the tire and put in a patch on the interior. I do NOT do the plug insert things. I had a very bad experience with a plug a LONG time ago, running 110 MPH in an old truck on 33" bias ply mud tires.......I've never used DT and like you I usually do it myself when it's possible to save the tire.
The centripetal force at that speed threw out the plug.