Cazi, I have used a Lupi on Bob and it worked really well and no, it has not caused any damage to him at all.

I have used a number of head collars in an effort to stop his pulling too and they work very well, especially this one.

But, as you may be able to tell ...

... he doesn't like it much!

So, if I am just taking him on the field, or somewhere there are not too many people/dogs, I use a harness that is very similar to the Lupi and it works really well too.
Here it is modeled by a Dalmation.

Bob doesn't mind it at all, we even have a 'one paw, two paw' routine worked out for getting him out of it without unhooking.

Chris