You can map F12 to any button on the CH.
Edit the map, place your cursor in the text box associated with the button you wish to assign to F12, right click and select 'record key strokes' then press F12, click 'Exit' and it will be copied into the text area.
Save the map, then click the download button.
Voila! F12 is now mapped.
I have F12 on my 6 o'clock hat on the MSFFB2