This is just a question as to why this would not work. If you are trying to force carb and don't want to go the Set it and forget it route, wouldn't the best option so as to not risk over carbing be to.... Take the keg, firgure the SIAFI psi, set it to that psi say 12psi, shake the crap out of it, let it sit for an hour, shake the crap out of it, let it sit for an hour, etc?? This way the beer never goes over the desired psi and thus never over carbs. I'm sure I'm missing something, but it seems this would be the best way to go about things??