Rick's solution with the Kodak Polycontrast filter holder is what I was talking about. Looks great and I am sure it works fine !
Here some images doing pretty much the same with a Beseler filter holder. They should not need much further explanation. Also some measurements of the Valoy II redfilter unit . . . centimeters, sorry! The only thing critical is where the bracket fits into the Valoy's arm. It really does go in there with the purpose of fixing it with the black screw. The width of 9 mm is exactly right . . .