Rated 4 out of 5 stars
Agreed – needs an icon for the tab, and delayed opening to avoid opening the download manager for very short downloads.
I also suggest to rename the tab. Instead of 'Custom Download Manager', I think 'Download Manager' is more fitting. Or even simpler, just 'Downloads'.
Everything else is very good. Just switched from 'Download Status Bar' to 'Custom Download Manager'. 'Download Status Bar' is for sure an excellent add-on, but I save 400 kb when using a little bit less convenient solution. It's never easy to decide what's the best balance between a speed and convenience for your browser. Too much and too bloated add-ons slow Firefox significantly down. But this add-on is lightweight.