Changing .Zip .Rar .Sit icons

I thought I could easily do this in Candybar... but I don't see it as being a possibility.

How do I change to default icons for .Zip .Rar. and .Sit files????

I know how to change an individual file (get info, paste, etc.) But How do I make the changes to affect icons for ALL files, new files, etc????

Thanks in advance for any help.

I would imagine you'd just replace the resource icon file in the correct applications package contents. Then relaunch the Finder

Of course I'd back up the original first.

I tested this with Rar Expander.