Here's a quick hack to disable compression, and automatically unset the compression flag.  Note that it only does this when you replace an icon, so basically, you'll need to extract all, then replace using this hacked RCO Editor.  Needs to be placed in the same folder as the normal RCO Editor.
I haven't tested this yet, so tell me if it works.
Also, I've made one or two changes since v1.14d, but I kinda forgot what exactly, so there may be introduced bugs.

Help this helps (By the way, uncompressed topmenu_icon.rco is like 609KB)