My wife is gearing up to go back to a CF-19 as her main laptop as her crappy $300 flex Lenovo isn't good enough (DUH...). They ALWAYS come back...

Anyways,
A CF-19 MK7 will cost WAY too much money. However, I can get MK4's for dirt cheap and I'm wondering if anyone has had 100% success in getting 8.1 to work on the MK4 including brightness control, front buttons, touch and digitizer?
I do have a few CF-19RDRAX1M units in stock I'm eyeing as it has the i5 CPU and is a dual touch model. As I've said, the wife WANTS Win 8.1.
Of course I DID see the MK3 thread here: viewtopic.php?f=3&t=1936 but know that the MK4 is a TOTALLY different animal!
Thoughts?