I have a + 4 with about 45,000 miles on it and no problems. I normally run it at about the 1/2 way point on adjustment settings. I have the tension set so I can reach forward and slap it at the top to move it lower if that is desired, however I have to stop and get off bike to raise it. I also have a full Vario on my Shadow VLX. It does a ok job , better tan what was on it previously . for the FJR I am going to try the Yamaha touring shield which is 4 inches over stock and 1/2 inch wider. It was cheap enough that if it works , great, if it don't I am not out a whole lot.
Yes the top portion of the vario can be purchased separately either in a clamp on version , or in a bolt on unit, or at least that was the options in addition to the full unit when I got the one for my shadow.
Eldon