http://www.pentax.jp/english/support/man-pdf/k-5-2.pdf
Last time I have searched for the whole document, there is no information of any for mentioning about the f/2.8 AF sensor for this "new" camera. So, the mystery about its layout and compatibility / usability with different lenses are yet unknown!
Speaking of the K-5II, IR has put their measurbation RAW(DNG) and JPEG files onto their website. So, pixel peeping time again! (Via 1001 Noisy Cameras.)
Related:-
What is the Exact Layout of the f/2.8 AF Sensor(s) in the K-5II/s?