The only description of the Hoya R72 - from their catalog - was, "Cuts off all light below 720 nm". I could not find a spectral transmisson curve in their literature - so I would *GUESS* that it was roughly equivalent to the more opaque (to visible light) filters.

I use a B&W 091 (? - think?) equivalent to a Wratten #25 - dark red, but one can see through it - with MACO 820 - hand held and with tripod ... this seems to work well.

Kodak HIE is sensitive out to 900 nm or so ... and the use of "heavily opaque" red filters (87, 89,...) is more common.