B+W filter on 17-40L and 24-105L
I have the 17-40 and, in an experiment, noticed very slight vignetting at 17mm with 2 slim filters stacked (UV + CPL). It was gone by 18mm. You should be fine with a normal sized filter, but a normal sized CPL might be an issue since they're normally larger than other filters. I haven't tested that theory though.