I have the top box on my c14.
Sorry for the ignorance, but I'm not sure what the "SW-Motech" kit is.  My bestem came with a metal mounting bracket.  I had to drill the holes in my rack to match the plate...

does that make sense.

i give the topbox a B+ or A-.  It is watertight, looks good, and the best deal for the money I found.  I think like $80 shipped from amazon...

I've been slacking on checking the forum now that we are hibernating up here...

I have the Bestem 929 box mounted to an aftermarket rack (bought the rack used and it was set up for a different top box), but I had to have my friend machine a custom rear bracket as the normal pyramid will not work.  If you look at my pictures, you'll see the back side needs to be straight and while the front needs to be sloped, you also need to add a small spacer which keeps from sliding rearward and unlatching.  There is also a lip in the opening you can't really see which needs to be there for the metal clip of the box. 

Overall, this setup works great.  I've had the Bestem box for about 3 years and I added the rack at the start of last season and it seemed to be fine.  One word of advice is there are exposed screw heads inside the box, so be sure to cover them with foam or at least duct tape or they will scratch your contents while driving.  I found that out the hard way with a spare helmet. 

It's interesting, on your set-up the opening in the rear latch faces forward, same as Givi monokey, however for it to work with the BESTEM it needed to face to the rear? I don't know if it's different for all Bestem trunks. Thanks for the photos.

The rear latch opening is facing rearward.  The last photo is taken from the back of the bike, the lighting is pretty bad.  It looks a little strange because you need that extra strip of material on the front side which keeps the whole box from sliding rearward and unlatching (probably why the Givi faces forward).  I could see if I can get the CAD drawings if that would help, I'm not sure if my friend kept them or not.