I use 35mm and MF, but I have a Photoflex Changing Room that you can get from FreeStyle [a shameless plug for one of our sponsers, item #25001] for $89.99. Their catalog states that, "You can even change 8"x10" film."
This is what I use for 35mm (though not necessary for this) and 4x5. My only, mild, complaint is it seems slightly awkward where the arm holes are located. I wish they were in the facing surface rather than the sides.