I haven't found them in the proper size for the Valk.
I have a set of them on my Vulcan and like them a lot.
If they make them in the right size for the Valk I'd run a set.
They must be made in the right size, picture is a Valk with that tire so who knows?
From what I can find on Shinko's website:
http://www.shinkotireusa.com/tire/230-tour-master They make the Tourmaster in a 150/80-17 front but not a 180/70-16 rear.
The closest rear size that they have listed is 150/80-16 which would be considerably narrower and somewhat less overall diameter than the 180/70-16.
I'm not opposed to running one on the front but I prefer to run a matched set of tires.