Hey, I found this video on youtube that shows Hewitt advertising a video fore the smash for cash event that will be held at the Australian open and it clearly shows him using a different racquet. At first I thought it might have been the Yonex V-Core Tour 89 racquet, but i realize that the racquet in the video is a darker red. It looks very similar to the Yonex RDiS 100 as well.
Here's the link below
If you pause the video at our 0:58 you will see a still picture of Hewitt with the racquet.