Nikon 77mm Circular Polarizer II - vignetting with step-up rings?

[puddleduck]

I can get a 77mm Nikon 77mm Circular Polarizer II pretty cheap over here (about £65 there or abouts) - this is the new super thin version, multi coated which is " Much thinner and lighter than conventional models to cut vignetting on Wide Angle lenses"

Why 77mm? Well its the ideal filter size for Wide Angle lens such as the Tokina 12-24 and Sigma 10-20 and also for my Sigma 70-200 f/2.8

Any ideas how this would work with stepping rings down to 67mm for the Nikon 18-70 DX and my 62mm Sigma 30mm? - my question is - if I use stepping rings will I get vignetting (I suspect I will at 18mm on the 18-70) on the corners?

[Boink!]

If you use a single ring from each lens to the filter (so you'd buy one 62-77mm and another 67-77mm) you should be OK. I think the more expensive step rings are thinner, but I have a 77mm infrared filter and with two step rings (67-72mm and 72-77mm) I can't remember if I get vignetting with the Nikon kit lens at 18mm.
I've no way of testing this tonight, though.