installing 3d Carbon rear lower skirts

[cpe]

Didn't get an answer in the exterior section so thought I'd try here. I have a set of these and had a question for anyone who has them installed. The inner fender liner bolts up to the bodywork about an inch behind the edge of the bodywork, but these pieces appear to be designed to mount flush. Was some kind of spacer needed to fill the gap where the 2 bolts mount this to the rear edge of the wheelwell? I don't see how these mount without needing something there. Thanks!