i managed a CHAT with a Focusrite tech.
 
before messing with the BETA drivers, he recommended 
 
https://support.focusrite.com/hc/en-gb/articles/207546695-Optimising-your-PC-for-audio-on-Windows-8
 
first.
 
he didn't recommend installing the BETA drivers outright without contacting tech support first.
 
he stressed ALL Windows updates need to be installed. which, funnily (or not so...), i have avoided.
 
so, i will take his recommendations first - install all my Win 8.1 updates and disable a bunch of crap per the above page.
 
we shall see. i will post.
thanks all
fred

ok!
 
DO NOT INSTALL THE BETA DRIVERS !!!
 
it will install new firmware that FAILS installation.
 
fortunately i was able to go back to the released drivers and mix control.
 
i followed the optimization directions - only one little hiccup.
 
so i shut down my Boss GT USB units, and replaced my 18i8 USB cable with a new, shorter cable.
 
so far so good.
 
lovin' it!
 

Happy days!