Firstly rev 17 is the most supported on this site.
but if you do indeed wish to install rev 20 this is the structure
then make sure if you are doing an offline install you put the relevant ios wads in the root of the sd
have you renamed the dol file to boot.dol?
that is the most common reason why a app will not show in HBC
It can function without the meta.xml and icon.png but you will get no icon or info in HBC just a blank button with the foldername.