Harry Lime, I would be keen to know how your experiment goes with the IR flash. I am improvising a similar system using a Nikon EM camera set on the manual shutter speed of 1/90. Mounted on this is a Vivitar 283 flash unit covered with a 720nm filter. This will be for photographing wildlife at night at some distance. I will have to do a test run when I have adapted the flash unit. I did try Efke IR820 film with a 760nm filter (on a weaker flash unit than the 283) and I captured virtually nothing. I think this was because the Efke is a slow film, even if it is more receptive to IR at a higher frequency. I am hoping the faster Rollei film might produce better results.