I have seen young ones do ok together. But it's still a 50/50 chance though. I have seen many large marine puffers be housed together for many many years with no problems. I think marine species of puffers tend to be less aggressive then BW and most FW puffer. But there always one that will kill or beat up on most fishes in the marine tank. But most of what I have seen over the years and in public tanks, they do very well together. But like I mentioned that it is still a 50/50 chance.
He who knows best knows how little he knows - Thomas Jefferson