If you have an additional diffuser, you might be able to combine it with a mask to even out the illumination, assuming there is a place to put the mask.
I thought about that too. Theoretically, the mask could fit in between the two discs if it is of the heat resistant variety like a Rosco product. I don't think it will take that though, I bet I get super close if not right on with just doubling the disks.
And it is not like having a mask in there will create issues for 6x6 or 35mm.
"I always put my fb prints in a filled aquarium on the wall.
No problem with dry down times..." APUG'r Willie Jan