Adaon

I'm trying to create a club that, when used, permanently penalizes the user's AC by increasing it two points (to fix a bug that gave a few of my characters an undeserved two-point bonus). 

I *thought* it would be as easy as invoking opcode 0x0 with permanent duration and parameter 2 set to 0 (All Weapons), but it only seems to penalize base AC, meaning the penalty vanishes as soon as I put on armor. 

I have no idea why this would be--Barbarian Rage uses opcode 0x0 with parameter 2 set to 0, and that penalty works armor or no armor. 

Can anyone tell me why the opcode's behaving so strangely and/or how to create the item in question (or otherwise impose a permanent AC penalty)?