I've got some fairly large slanted Vikings on my 2012 - and yes, the "universal" mounting bracket is a lie in this case. The instructions for the S40 tell you to mount to one of the forward fender rail holes and the rear fender rail hole, except that there isn't a rear fender rail hole - it's internal. I drilled a couple of new holes in the fender rails and mounted the cases to those. Have to take the fender rails off now to get the cases off, but it's not hard once you've done it a couple of times. And they're rock solid.