Here is a note from Mike explaining why it has to be the way it is.
http://www.titleist.com/teamtitleist/team-titleist/f/9/t/4784.aspx
I just read that the tip is .335 on the hybrid
It sure didn't work for Adam Scott this week...
I've used a "Sternum Putter" messing around at the shop, but never one that goes in the gut like Freddy C.