I recently suppressed a 16" FAL (rifle length gas system). As noted above, an FAL is not the quietest setup, but if done correctly, it's lots of fun.
I did another approach to adjusting the gas for the suppressor. I wanted a similar quick adjust suppressor setting as is available on ARs, SCARs, etc., so modified the gas adjustment collar instead of the gas plug. Cut a steeper angle in the gas adjustment collar so that the full range of adjustment was ~120 degrees, attached a small adjustment lever to the collar so that it has range of travel throughout the entire adjustment range, and now can switch between suppressed and unsuppressed with a quick push of the lever using 1-2 fingers. Left enough adjustment on the reduced bypass end so that I can adjust for varying ammo pressure levels while shooting unsuppressed, and just push the lever all the way to the stop on the max bypass end for suppressed shooting. I still get more vigorous ejection with a suppressor (would have to drill out the barrel more for a larger bypass port if that was a problem), but the gas setting is still acceptable to me as is as I have no issue with blowback in my face even when shooting suppressed left handed. Prior to the mod, if I didn't open up the bypass enough I'd get almost sick from the amount of gas in my face from shooting suppressed, and wasn't able to comfortably shoot it suppressed left handed even when I did crank the bypass up.
Now this approach might result in a little more noise than a reduced port gas plug (not sure if to a noticeable amount, though), but I'm happy with how it works, and I don't have to keep track of an additional gas plug and have to change it out for suppressed shooting.
Slightly off topic, I've happily discovered no shift in POI between suppressed and unsuppressed shooting - that has not been the case with most of my other suppressed rifles. And I've gotten very surprising group sizes - smaller than I'd expect from an FAL. Probably little to no impact from the gas mods, though - I'm assuming it's more likely due to the shorter (16") barrel.
In full disclosure, it was actually a local gunsmith friend who performed the above mods for me (I miss having a garage with my tools set up in it
). We'd discussed what I wanted and how I wanted it to work, and he made it happen. He's already repeated it for others who have seen my rifle and liked the approach.