Well, that's odd then.
In 1.4 (for me at least...)
For annexed territory, there is no mimium revolt risk, or rather, its set to 0. With enough supression you can then reduce it from the default 10 (degrading over time) nationalism value. Also, i beleive that supression works best for the tile its on, and at least for a few tiles around it. Will try and get specifics on that later, can't boot HoI3 this second to test.
As for weight of supression, well. With an entire inf army (60ish brigades) stacked on a single tile, i was getting a supression of about 15. I had messed around with garison/MP divisions a little bit before, building 1gar/3mp. Placed about 10 of these throught my balkan conquests, but they had limited effect on their own, perhaps a single point of supression on their immediate tile. They were only base tech though. Supression values might need to be improved tbh.
Ok, done some testing.
Firstly, went back to my infantry example, was actually 10hq's, 18mtn, 54inf, giving 14.54 supression. took away the hq's and the mtn and got 10.79 supression from the 54inf brigades alone. This gives us approximatly 0.2% reduction per point of supression. I also noticed that in every province that was 1 or 2 tiles away, the supression was half.
Basically, each supression point (unit trait) gives you .2% reduction in the units province, and 0.1% reduction in the surrounding provinces for two tiles.
After this i build some gar/MP/Mp/Mp divisions to check, and with base techs (gar supression is 2, Mp supression is 3), their 11 supression gave 2.2% reduction to revolt risk. 5 of them stacked gave a nice 0 revolt risk on their tile, 10 stacked gave a nice 0 revolt risk for their tile and the surrounding ones. You could also make pure Mp divisions, 4 or even 5*mp, this would probably be more effective if you knew you weren't going to be facing any attacks.
Also, the improved security units reasearch is essential. Mp starts out with a base supression of 3, however the research, which is quite easy, going 2 years ahead of time shouldn't be a challange, raises it by 2 a pop (in other words, a 42 teched Mp brigade has 7 supression instead of 3, or 1.4% reduction per brigade). So yeah, tech them up
Finally, as for optimal placement, i don't have the slightest clue. There's probably one though. For now i'm thinking of trying two mp/mp/mp/mp divisions on a tile, then the same again 3 tiles away, so that they fully supress thier tile, and the overlap from the next one fully supresses the tiles between, but it might be inefficient.
