Hi all, just a quick update. We are now working with a trainer on basic obedience stuff, with a goal of moving into some agility work. Our runner, Delia, has surprised us with her "trainability," and though I don't think we're ever going to trust her to roam on her own, I do think that we are going to be able to work on her "come" and "stay" commands to get to the point that we feel confident we will be able to successfully call her back should she accidentally get out. Next week we move on to work with the 50 foot leash, so it will be her first real test of listening to our commands when she has more freedom and distractions.
I'm so glad this thread has been helpful for other people to compare notes on strategies. For what it's worth, our trainer didn't think the electric fence would be that useful for Delia, because as a collie mix she has the thick neck fur.