What I do is:
Under ArmA2 folder create a FOLDER called x
Under x I create a FOLDER called @chally
Under x\@chally i create a FOLDER called addOns
Under x\@chally\addOns I put all the *.pbo and *.bisign files from the addon.
Then I add this to my ArmA2 shortcut:
This way I keep ALL my mods under the x folder so I can really easily save them during a reinstall or replace them as needed since they are all under x.