Jalal - Good to know it doesn't vignette on the 16-35L. I've been thinking to upgrade from the 17-40L. Ben - how much sharper did you find the 16-35 over the 17-40?
For the Schneider, see post #269 in this thread. The Schneider is thicker and may not fit in the Lee holder:
Jamil, I'm actually not 100% sure if it does or doesn't so don't quote me. I thought I read in this thread somewhere that people did not have issues at 16-17mm. Someone please correct me if I misspoke.
I noticed the 4mm thickness in that post which is double the Lee. I know Lee sells a 4mm guide for their FK's so I planned on picking one up if I went with the Schneider. However, some reviews on B&H mention the stubs on the 4mm guides not lining up with the indents on the 2mm guides. Idk that it would really deter me since you have a screw holding it down regardless. I'd also have to double check to see if I need the longer screws they sell as well.