Welcome to the forum! I have a large GSD and a small Chihuahua who have been living together in "nearly" complete harmony for the past 10 or 12 months. What exactly do you mean by a stomping issue? Is your GSD pawing the little dog? With mine, I watch and tell them to calm down occasionally, but for the most part the GSD seems very cognizant of the smaller dog's size and seems to be pretty careful with him. They play though, and surprisingly play like you'd expect 2 dogs of the same size to, showing teeth and comparing bite sizes, it's really quite comical to see LOL!
The other day though, the GSD was seeking a squirrel and jumped up on a tree trunk trying to get at the squirrel. When she landed one of her feet came right down on the Chi's back and I was very worried he'd be severely injured!
So the size difference can be a problem! Fortunately my Chi wasn't injured, but it could have been, so caution is needed! I guess how you handle it depends a lot on the dogs involved though. And it's certainly worth noting that it may or may not work out well...some big dogs just plain don't like or respect small dogs, while other seem to do it naturally without much guidance.
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain