I picked up some Maco 820 in the fall from the local Maco distributor here in Canada. They recommended using a Rodenstock RG715 filter. I haven't had a chance to use it yet but the filter sounds like your Hoya RM72. When held up to any kind of light you can just barely make out shapes. I think a focus first then attach the filter operation may be required. I have a friend that also bought this filter and I will ask him if he has any comments on it.
I have used Kodak HIE and Konica 720 with a #25 filter for hand held with some nice results.