What are you guys using for ND filters, screw ons or slide ins? It seems most people feel that slide ins perform better but i really dont want to add the bulk associated a slide in system. Even if im not backpacking and just out walking around i still have to lug it all around. Screw ons seem more streamlined and lighter. Ive mostly been using a 16-35 lens and some people are reporting vignetting issues at the wider end with a screw on system. Can i alleviate this with getting a larger filter and a setup ring? Any rec's on particular filters? Looking at both 6 and 10 stop filters.