Sort Completion Result elements

Hi, I always had problems with sorting the completion result elements, could you point in the right direction direction for doing this?
I have an extension point for "completion.contributor", I'm adding my LookupElements to the result and that works fine, but I want to show my elements on top, is this possible?

I've tried adding an extension point for "weigher", and I'm using a code like this:

public class MagicentoPhpWeigher extends CompletionWeigher {

    @Override
    public Integer weigh(@NotNull LookupElement element, @NotNull CompletionLocation location)
    {
        if (location == null) {
            return null;
        }

        Object object = element.getObject();    // we can pass any object inside the LookupElement creator in our MagicentoXmlCompletionContributor
        if(object instanceof String){
            String reference = (String) object;
            if(reference.startsWith("magicento")){
                return -100;
            }
        }
        return null;
    }

}

for some strange reason this was working fine in PHPStorm 5, but not in v6

Thanks !
Enrique.