Using step up adaptors

Due to cost and lack of availability I need to buy a step up ring from 49mm to 77mm to use my cokin z pro filter kit on my 35mm lens. I thought it may be a good option considering 49's are impossible to find and I already have the ring adaptor 77mm. Anyone had experienced with these step ups? Problems with vignette get?

If it is a 35mm lens then one should not have a problem with most of the lens varieties in that focal length, with items such as vignetting.

For that particular filter size (49mm filter), the best choices for variety are places such as ones located in NYC