Barrel Refermentation w/ Bugs, pressurization question

Hey guys,
I've got 4 20l oak barrels that I was going to toss a Flemish Red, Flemish Brown, soured Belgian Dark, and a RIS into, but I'm going to be out of the country for a few months and am just curious if the refermentation activity by the bugs in the 3 sours is going to pressurize the barrels. Because of their small size, I'd be hard pressed to find a bung that would fit an airlock and still fit the bunghole (I know that statement just set me up for all kind of jokes), but is this something I need to worry about, or do I just ferment way down first to avoid exploding barrels?

If you have access to a drill you should be able to make a hole easily if you're worried

Really the issue is the stave width, it seems like if I enlarge the hole enough to fit a small bung, there's not much width left on the stave for structural support. Will definitely see what I can do though. Got in touch with Vinnie at Russian River and he definitely suggests an airlock of some sort, just need to figure out how to incorporate it in my barrels.

How small is the bunghole? I use a small rubber bung that gits the grommet hole in a drilled bucket lid. I doubt it could be any smaller than that and have any function at all.

Oh, it's only maybe an inch across and the whole stave is maybe only 2 inches. I did find a solution that seems to work strangely well. I cut off a short 1" section of the silicone tubing I use for hot transfers, a short 1" section of the vinyl tubing I use for racking, it turns out one fits just inside the other, and with an airlock in the middle, the whole thing fits perfectly in the hole.

Do you have any glass carboys? The stopper you use to hold your airlock in those should fit fine, its what I have in my 5gal barrel. If not, you can just drill a hole in whatever bung is on it