I have anodized rims on my Redcay (currently Ambrosio Synthesis Durex, but something else originally).The brakes have always screamed like banshees. It's been hanging in the basement for a long while, in large part due to the noise. Some time ago, I acquired a set of Modolo Sinterized pads & holders. My thinking was they might help wear down the anodizing on the brake tracks. After three rides, totally about 130 miles, I couldn't detect a difference than when I was using Campy pads (well, Kool-Stop) and holders.
So, on my ride today, I came to the conclusion that I should explore the possibility of adding some toe-in. It seems to me that many toe-in recommendations over the years involved twisting the calipers. That was something I wasn't willing to do (maybe for horribly cheap stamped steel calipers, but not for my Campy Record parts). I had received the Modolo parts for free. They were new and huge, so big I could only squeeze them between calipers and rims by sanding off some material and running with the quick releases wide open. I was willing to sacrifice them for the sake of science.
I wound up tapering them so the front is about 1.5-2.0 mm thicker than the back of the pads. The resulting profile looks pretty crude, but since these are going to wind up in something like the Box O' Crap, I didn't really care.
I used a sanding wheel on my Dremel. This generated a ton of brake pad dust. If you do this, WEAR YOUR MASK!
I haven't gone on an actual ride with the "new" pads yet, but did go up and down the street. Blessed silence! Once I get some new Campy holders for the Redcay (of course, I forgot what they were for and sold the originals out of my parts bin.
I will also have to rig up some sort of jig to make a cleaner, smaller, and more reproducible cut. For the time being though, I won't be scaring the bejeezus out of anyone in my immediate surroundings.
Edit: I don't recall anybody explaining exactly why adding toe-in works, but I have a hypothesis (though no experimental data to back it up, so it's not a theory). I think when you squeeze the calipers they twist ever-so-slightly. As they try to return to their prior shape, they exert more force on the fronts of the holders. Some of you engineers who aced your dynamics classes in college feel free to chime in.