Both Mozilla and Chimera keep their master settings in a file called prefs.js. It's well known that one can insert certain settings from Mozilla's prefs.js into Chimera's prefs.js, and have it actually work. As far as I can tell, the cache location setting is one of those certain settings.
Here's what my setting looks like when I change my cache location to a folder called Downloads in my home directory from within Mozilla (all one line, no spaces after the ","):
user_pref("browser.cache.disk.parent_directory",
"AAAAAAEqAAIAAQV..[characters trimmed]...AA==");Don't just use the above string, though! Launch Mozilla, change your cache location, and then copy the actual user_pref line from your Mozilla prefs.js to your Chimera prefs.js. Chimera's prefs.js can be found in ~/Library -> Application Support -> Chimera -> Profiles -> default -> random, and Mozilla's prefs.js is in ~/Library -> Mozilla -> Profiles -> default -> random, where random is something like "fesm4ts2.slt".
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021211052821617