Yes, the angled barbs is a good idea.
You may want to go like on "top view 2" because of RAM sinks restrictions on many boards
AGP/PCI slots clearance is standard, check
http://www.formfactors.org , ATX spec 2.1 page 12.
With angled barbs you should cover 1st PCI slot but not the 2nd one, so it's ok.