I agree that there are too many variables (KH, needle value type, ...) to make bps a very accurate comparison. But, I also feel that it should put you 'in the ballpark'. When I was running my CO2 at 24/7 (about a month ago), I typically had to run at 80 bpm to get my CO2 levels to 30+. However, prior to adjusting my spray bar to reduce some surface agitation I was closer to 130 bpm. So, if you're at ~60 bpm and you've got CO2 levels >50, that sounds almost too good to me.