Somebody correct me if I am wrong, but ModAv may be temporary, but still requires another ModAv command to remove the additions made by the first. So in effect, a single ModAv acts like a permanent skill adjustment. ModPCAttribute works on attributes like strength, intelligence, etc... I think you are looking for http://geck.gamesas.com/index.php/ModPCSkill.
For me personally, I would like a clarification of the ModAv command as I have used it profusely to modify the player skills in my mod and now I am doubting weather this was the right thing to do. It seems to have worked they way I wanted, but I do know that when I used that command to raise the player's health, there were problems. I had to make the modifications to the player's health be hidden perks.
It seems you were doing the right thing - I looked at the Bobbleheads, and they DO use a script and they use ModAv. So i'll just use that, worry free
Thanks
scn BobbleheadREPRScript;This is a Bobblehead script for the Collector Bobbleheads located in game;On pickup, you recieve the motivational phrase and the appropriate buffshort DoOncebegin OnActivateif IsActionRef player == 1 if ( DoOnce == 0 ) ShowMessage BobbleheadREPRBuffMessage ;This is the corner buff message Player.ModAv Repair 10 ;Mod the perm. pool so it sticks Activate ;Allow item pickup Set BH01.Bobbles to ( BH01.Bobbles + 1 ) ;Add 1 to master count Set BH01.Carrying to 1 ;Tell the script the Player has one or more Bobbleheads (for display case) ModPCMiscStat "Bobbleheads Found", 1 Set BH01.HaveREPR to 1 ;Set the variable for Display Case if ( BH01.Bobbles == 10 ) Addachievement 49 elseif ( BH01.Bobbles == 20 ) Addachievement 50 endif Set DoOnce to 1 endifendifend