Kinematics for XYZAB mill

Hi guys, I am a bit lost on how to configure a kinematics module for a 5 AXIS XYZAB mill  something like this:
 
Any pointers or examples would be really appreciated as I'm not quite sure where to start modifying the provided linematics modules.

Hi,
i never set up a 5 axis mill with linuxcnc, but this kinematic is not right. B-axis usually wrapped around y-Axis- The C-Axis is wrapped around Z-axis. So the kinematic must be XYZAC and i think we have some examples here
linuxcnc.org/docs/html/motion/5-axis-kinematics.html

I think the B axis is correct if it is assumed the swing arm is horizontal in its normal position. eg. it rotates between 6 clock and 12 oclock.  Its not XYZAC in that case. I nearly made that mistake.
And yes @chris, I've never set a 5 axis up either!

tommylight wrote:

At 12 o'clock it will be inside the spindle, or the spindle will be inside the turnion/turn table, whatever is fastened better wins.

I don't think such comments are useful.
What we need is  XYZAB kinematics no matter how foreign that sounds to you. 
Andy indicated its possible on this thread
forum.linuxcnc.org/10-advanced-configuration/41281-5-axis-xyzab
I need help in this area.

Let me put a bit more mud in the water...

I think A and B are right.

The thing is that we are used to have X axis left and right but in this case it is front and back (see legend). The A axis then definitively wrap around the X axis.

Then if you put the B axis at 9 o'clock (horizontal) instead of about 7 o'clock like tit is on the picture you will clearly see that it is in fact rotating around the Y axis.

Note: NO, you cannot put the A axis vertical and then use the B axis as a C axis simply because rodw mentioned that it rotate between 6 and 12 o'clock. (Is that muddy enough?)

What do I win ?

@rodw:

This may be a crazy idea but if you modify the machine in such a way that the arm connected to the A axis rotate from 3 to 9 o'clock  you will then have a XYZAC machine since the B axis will then act as a C axis (visualize with the arm at 6 o'clock). (There's also a bracket on the right of the legend that is interfering with such a motion)