The max amount of ram an 32bit app can use is 4.2GB something. I have never seen any game using more than 1.5GB RAM. I remember seeing ROF using that but in average no game I ever played used more than 1GB.(Guess if Crysis 2 uses more than 1GB ram).
I guess if someone had 2 GB there can be problems since OS take some ram.
If Luthier said 2.6GB is the maximum amount of ram used I don't think people with 4GB can have any problem related with the RAM as long as they keep other apps closed and just running the sim and teamspeak.
For those interested on clearing some ram before playing IL2 COD. There is a software called AlacrityPC. I use it everytime I play games and leaves me 3.7GB free of 4.0GB.
http://alacritypc.kensalter.com/