I would say, regardless of your training methods, at some point, you are going to have a conflict occur probably between your 2 and 16 month old males someday. No multi-dog household is completely quiet and calm. Dogs can't talk like we do and the way they settle disputes is often through growls, posturing, a nip here or there, etc. The thing is to allow it and not worry about it unless someone is getting seriously hurt by the other dog. The more you break up small disputes between your dogs, the larger the conflict will grow due to their frustration of never being allowed to handle it themselves.
Now I never saw them do it, but I can probably promise you that at some point when I wan't home and my Saint and Malamute were home alone, they probably had some good squabbles to establish hierarchy and figure out what is and isn't okay with each other. Even now, my females will have minor disputes. I never break it up unless someone is getting seriously hurt. It is of utmost importance to let the dogs settle things is what I believe.
Conflicts are inevitable. Yes there may be growls which I will (and do) allow IF it's warranted. Such as stepping on someone's toes, being too in your face etc. Posturing, staring intensely, mounting and fighting are just not acceptable in MY house. I am the one that steps in if things are getting out of hand and I will never let them "work things out" between themselves. They count on me to be the rule maker and peacemaker. When I do have a conflict I reexamine what went wrong and how I can make sure it doesn't happen again.
The book I referred to in my other post is called Feeling Outnumbered? How to Manage and Enjoy Your Multi-dog Household. It's like 10 bucks.
Some of the Chapters are Life is Not ALways Fair and That's Okay. The idea being dogs need to cope with the frustration of not always getting what they want whenever they want it and giving up on treating your dogs equally at the same moment, all the time in an attempt to be fair.
Chapters on Status, Body Blocks and one called When Someone Else is Belle of the Ball are great. I used body blocking aallll the time when I first started teaching these guys not to be so pushy. The belle of the ball chapter deals with teaching your dog how to handle watching another get treats and praise and attention. Very useful for when you're at the pet store or when you're out for a walk and the mailman wants to pet the other dog.
Staying Away From Trouble: Prevention, Thank You for Not Fighting or Making Threats in My Home could be useful to the original poster. And while this post is old I hope it it can still help someone out.