Hello Alun,
I have used the Lee RF (now renamed Seven5) filter system both with the Leica M9 and now the Sony A7r. To do so on the WATE I use the 67mm Leica adapter originally marketed for the M8 and the equivalent Lee adapter ring for the filter holder.If used together with an UV/IR filter (tempting because of the protrusion of the front element of this lens) it produces noticeable vignetting at 16mm. Removing the filter resolves the problem. I find the WATE hood provides sufficient protection for the lens,and when not in use the hood cap gives additional peace of mind! The filter holder design means that reflections from the back of e.g. the polariser can be troublesome unless you interpose your head or hand or 'black flag'. A cut off sock fitted over the lens and pulled forwards onto the rear of the filter holder seems to work well.
Best wishes
Andrew
