IR Preparations

I have a plan - to shoot IR with an old analogue camera.  I am just wating for sunny days to get back.  I tried a Hoya R72 filter on my Sony compact with its aperture set to 5,6.  Without the filter I got an exposure time of 1/400 s and with the filter 3,2 s.  That is about 10 f-stops difference.  The camera's sensor isn't sensitive to IR-light so when using film I think I'll start with "only" adding 5-6 f-stops.