Tried two of these with my guys...a bungee type and a regular.
Both of them ended up under Danny's tail way too often...and Dan comes to a dead stop if there's something under his tail. I know it's because of the way they tend to wend their ways around each other...especially when we stop...but those leashes got donated.
Even if normal walking works with these, if one of the dogs gets excited (like the 7 month old), you have basically no control over the dogs...at least no direct control of the energetic one. If your dogs are perfectly trained and never deviate, this might be a good thing. Mine are trained well but not to the point where I'd use one even if we didn't have the Danny/tail thing going on. If you're going somewhere where you won't meet other dogs, perhaps you won't have an issue.