My daughter demo'd an H4 and I demo'd and H6 last fall. I was suprised at the open string pattern they had. After studying some pic at a Wimbledon Web Site, I noticed that Venus and Serena's racquets were 20x19 (not 16x20 like we were demoing) with a tight pattern in the middle.
http://championships.wimbledon.org/...gepages/2003-07-05/200307051057417299864.html
I eMail'd Wilson about it and they said that Venus and Serena really use the H4 and H6, but they get them un-drilled so they can midify the pattern and modify the weight.