I've got recently Hassy HC 50-110, which has 95 mm thread and I also have lee filter system. Purchased adapter ring and found that if there is any extra filter like UV attached to the lens, on 50mm with lee system it gives some slight vignetting. Without UV - it's OK. In BHPhoto description it said "for long lenses" but comparing with other adaptor rings it doesn't look any thicker.
The concern is that I'm planning to get 28mm, which is also 95mm. It will definitely vignetted. What are you using in this combination? Is there any 95 mm Lee adapter for wide angle?