Not worth a try at all, IMO. You have things working well now and adding another porc could just mess everything up so quickly. I would say 99% of the time one ends up dead eventually. It can take years but it always seems to happen. They just do not get along once both are adults. It often works when they are small (especially when one is much smaller than the other) but once they get close to the same size, they get territorial. I have unfortunately tried it
Please don't take this the wrong way but I would say for some people it may be worth a try but knowing you and how much you LOVE these fish, I would not do it. Its just too much of an experiment...especially long term. I think if your tank was a big bigger, it may work but a 280 is pushing it.
One of the worst parts about porcs fighting each other is that they seem to go for the eyes first
At least mine did...you can imagine how messy that was. They were together for about a year before the real fighting began. But that was also only a 180, so obviously way too small for two adult porcs.
The one way it can work is the same way some people keep many angels or tangs together and that is to severely overstock the tank and never allow the fish to claim territories. I guess if you had like 50 fish in your tank, the puffers would probably leave each other alone but tanks like that are so horrible IMO. All your doing is keeping the fish stressed 100% of the time so that they don't single other ones out.
And I know you would never do that
