The Ilford SFX filter also makes a good filter for the Konica film, and possibly the Maco, and may be easier to get hold of for tests.

I'm not convinced by the notion that flash always gives useful infrared, as i've just been checking with studio flash and a Fuji finepix (that i've just bought in part for verifying the lighting balance of a flash system - instant feedback should shorten the learning curve). The finepix will record an IR image through the SFX filter in sunlight, but records nothing with the flash (even though the same settings give a completely white image without the filter). Has anyone here had success using flash and IR?