I totally agree regarding the training. I was finding that walking them individually was fine and for most of the time they would be walking to heel. When taken out together all hell breaks loose!!!
The solution we were being told by trainers was not to take them out together and they have been fairly negative about owning litter mates of such a large breed. To me that was not a solution and I got them as part of my family and we all go out together as a family.
The dogmatics are allowing us to do other elements of their training when out rather than constantly focusing on the pulling. Also, they seem alot calmer when we are getting ready to go out which is also a bonus.
They now put their heads in them so they must like them and it must be more pleasant for them not to be choking themselves from the pulling. I've also noticed a lot less slobber when walking!!