I just bought an AC500 to convert into an HOB fuge. I originally had a fuge built to go under the tank beside the sump, but have since decided to go with an HOB fuge for pod propagation since I have no intention of using the fuge for nutrient removal. I'm going to use the old fuge for an RO holding tank for an ATO.
Ok, I'm rambling now...anyway, I'm not going to make any permanent changes to the AC500 just in case I want to sell it one day. I'm going to go to the craft store and buy that mesh people use to make needle point crafts. I think that should do the trick so I don't have to mutilate the media basket.
Please do post some pics of what you decide to do to yours.
Oh, and no a fuge is not a skimmer replacement.