I also risk the sarcasm of those who think shite all over the back of the bike, not to mention legs, arse and bike seat, is some sort of inevitable result of riding a bike.
I've done thousands and thousands of miles on all sorts of bikes in every kind of weather all year round for many years, so I feel I can speak with some authority.
My 12GS is without doubt the worst bike, in this respect, I have ever used.
I'm not knocking the bike, I love it !!!!
I will make the following comments:-
The shite catcher does work - I ran without it for a while, and the topbox and back of bike got even more covered in shite.
I think the shite that gets thrown up onto the back of the top box comes from the bottom edge of the shite catcher. I've fitted a "number plate extender" (see pics) albeit not a Wunderlich one, (it's a bit of Triumph Tiger actually) and this itself remains clean, so it's not doing anything, and makes no difference to the shite on the topbox.
I may try a short extension to the bottom of the shite catcher to see what effect that has.
I had a Pyramid hugger on for a while, but it rubbed the Tourances, so that went back.
BUT - it did make a considerable difference to the shite on boots and legs, so at some point a hugger is probably on the cards.
Just to add some weight, possibly, to these comments, I've done 9000 miles since March 1st on my '07 GS