Yes. As I wrote in my first post, you should NOT unpack the archive, but clicking "open" is just that. Save the mod somewhere, make yourself an "Oblivion mod archives" folder or something like that. Then navigate there from the "Add archive" dialog in OBMM.

Btw, my downloaded Oblivion mods folder is currently 38.8 GB, though I don't have all of them installed...

Okay Now I get it, thanks TheNiceOne. Ill edit this later to tell if it worked.
EDIT:I got Deadly Reflexes working! Thanks TheNiceOne! Now I know how to install any type of mod, unless theyre is another type.