We regularly work the rear uppercut on the "reinforced" pad.
This is a close range unique kind of KO if you an create the angle and optimise the opportunity.
I have referenced Tyson knocing out Bruno with this punch.
If you haven't seen the match, you can here on You Tube:
http://www.youtube.com/watch?v=NC1KgO-ZoLM
forward to 5.30 mark and see the KO. It's replayed in slow motion several times from different angles in slow motion.
Imagine what you can do when you've perfected this punch!