Robert in our forums has posted a great guide on how to convert the X98 Pro (k9C3) model which comes in only Windows 10 to a dual boot Android 5.1 and Windows 10 image. The guide and download files are here: How to dual boot Android 5.1 and Windows 10 on the X98 Pro . And you can also download the files from the X98 Pro downloads section.
Update: After using the rom for a bit now, I can report it has sleep issues and eat up the battery when the screen is off. Seems it will not go into a deep sleep. The rom is clearly a beta release, so keep that in mind. You also lose your cameras if you flash the dual boot bios. So I recommend to hold off for now. A new release Rom has also come out today in China.
I made two videos to help people converting their X98 Pro’s to dual boot.