After searching up and down, here's an easy way to get the job done: (I have a new mbp retina with 750GB SSD) 1. Figure out the space you want for your Mac partition (A), your shared data partition (B) and your windows partition (C). In my Case A=250GB, B=150GB, C= 350GB. 2. Use BCA and partition the windows partition as C, leaving the MAC partition as A+B. 3. Boot back into OSX and split the Mac Partition into 2 using Disk Utility. The split should leave your Mac partition as A and your new MAC format partition as B. 4. Boot into Windows USB Stick and install into C. 5. Download trial of Paragon Hard Disk Manager 12 Professional Demo (English) 6. Use HDM to convert the Mac Partition (B) to NTFS. 7. Buy a NTFS driver (I used the paragon one) and install it on the OSX side. 8. Check its working and then install Bootcamp drivers (in WindowsSupport directory) on Win8 side. 9. Voila - you are done. A shared Data Partition (B) and fully working Mac side and Win side. eom.