I have already 4x6 Lee Grad. ND filters. Since these were so large, I never bought a holder. But now I'm thinking of getting some B&W resin filters(yellow 8 and eventually a red 25). A couple questions? I have already some older glass 55mm thread size #8 and 25. I only have one lens, a 58mm thread size 180mm lens, so was wondering if for time being, would I have any vignetting using these older filters on my lens? If I need to buy some new ones, what size of the resins should I buy? 3x3 ($11), or 4x4($58)? And lastly, and I'm surprised how expensive they are ($110), would I need to also buy the holder for these smaller ones? The 4x6's were not difficult to hold in place, but not sure about the smaller sizes.

Thanks,
Chris