Ha, it made me
that I had a mention! 
I would keep a eye on them closely, any teeth chattering, nose ups, more harassment than usual then be ready with a spray bottle of water and a towel and watch them like hawks! (Spray to squirt them, towel to chuck over them if they need separating).
Boars need a lot of space to stay settled. My two were separated at night after they first got arsey (same set up as 70 with a grid), and went in their day pen fine.
They got separated permanently after they had a mouth to mouth fight and drew blood. I have since tried to get them back together resulting in more blood and some very sorry piggies :(
Are they going to be in that cage all the time? Do they have a day run? Abit of variety may help.
A bath may also help, they can be arsey with being wet rather than each other. 
Tbh loud continuous teeth chattering was what gave my two away. Not just the usual 'feck off I'm eating' it was a 'feck of or else
' . You will know what I mean if they do it, its a awful sound :( . If they draw blood then give them time to cool off and take it from there. Like I said, I have tried with my two but it hasn't worked, they are happy with their side by side set up for now. I haven't had the balls to try again since especially as they still piss take each other through the grids 
Make sure you have 2 of everything, water bottles/food bowls...everything!. Maybe take the house/hidey (one that sits full length across the bars?) out so there is nothing that they can be territorial about. If one gets under there and the other one wants to but isn't allowed, it could cause trouble.
Lots of hay and plenty of floor/run time and hopefully you will be ok!
I found this very helpful!
Good luck! :)