I have a 4x4 matte box (2 rotating holders), and i am trying to get some Formatt graded ND filters for a landscape shoot in sunny California desert. I am thinking they will come in handy. They don't make them in 4x4, only 4x5 so that you can adjust where the horizon line falls. Makes sense. But, how do i make these fit my 4x4 holder? The adjustable 4x5 holders are too thick to put in a matte box.

B&H has Cavision 4x5.65" matte box holders for $56 (http://www.bhphotovideo.com/c/product/627071-REG/Cavision_MBH4X5_65H_MBH4X5_65H_4x5_65_Metal.html) and Redrock dual 4x4 / 4x5.65 holder (http://www.bhphotovideo.com/c/product/672534-REG/Redrock_Micro_4_002_0003_microMatteBox_4x4_4x5_65.html). Would either of these work? What about that extra 0.65" on the long side, will the filter fall through?

Any other ideas/solutions? Circular filters won't work, i have too may lenses with varying diameters, even as small as 22mm.