There are a lot wiser people on this board than I am but I will give you my experiences. If you search Wheeler you'll see photos to back up the relationship between Wheeler and Walker. They were absolutely the best buds ever. They would share their toys, went swimming together, slept in the same rocker, one on top of the other. They were always touching each other. I can send you tons of shots of them playing and racing and having the best of fun.
Walker was about 1 1/2 when I bought Wheeler. Wheeler was taller than Walker but Walker was the alpha dog. Wheeler was Mr. Happy Go Lucky. By age 3ish and 1 1/2ish I thought I could see a problem creeping in -- just once in a while. They still loved each other. I thought for sure I had control of them except twice. The first time it was maybe over a frog, who knows. I was not there but you know, it would not have made any difference. When they turn on each other it's immediate and horrific. Walker although the alpha took the brunt of the injuries. I remember he had something like 70 stitches up his leg and on his chest. Wheeler didn't have to have any stitches. Of course I separated them in crates and they wouldn't even look at each other for days. The second time was about 4 years later. Mr. Goof Ball Wheeler went flying off a retaining wall and accidentally brushed Walker. The fight was on. I was maybe 100' from them and it would not have made a difference had I been 10 feet away. They tore each other's throats open and the top of Walker's head was cut from ear to ear.
Watching that almost gave me a heart attack. I couldn't scream loud enough to stop them. Luckily a worker was here and he took Wheeler's hind legs and I took Walker's hind legs and pulled them apart. (I believe that is the safest way to separate them. I have heard fireworks work but I don't know.)
After that, for about 3 years, they never went out together unless my son and I were both with them. Wheeler also became alpha and Walker more or less bowed to Wheeler--first out the door, etc.
I know others on this site have successfully kept males together. Elly and her husband are successful at it. I wasn't. My boys never met a stranger and loved other dogs. But twice over something so very minor, the fight was on.
So not for the world would I put my own Doberman male with another Doberman male. I just won't run the risk again.
I don't like guilt feelings but my dogs look to me to feed them, give them shots, etc. I believe it's my responsibility to do my best to keep them out of harm's way as much as I can.
You have a tough decision. Good luck.