ECA Stack
I've been using Ephedrine for over 20 years in ECA stack form up to three times a day. The most E I've taken at a time is 50mg. But I knew a couple of power lifters years ago that took up to 150mg over a period of about 3 hours before competition. These were massive guys who weighed in the high 200's though. My guess is that the amount a person can tolerate is dependent on how long they've used it and what kind of tolerance they have to it. I know I've had some 'heart flutters' on it but that was usually when I mixed a lot of other stimulants with it. These days 25mg with 200mg of caffeine will speed my heart up but the BP never rises.
But don't take my advice. I've heard of other undocumented cases of some young kid dying on their first hit of the stuff. It may be true. They may have already had a pre-existing heart condition. Maybe this sounds cold but the Eph probably just knocked them off a couple of years early.
But if you listen to the FDA warnings it's a sure fire killer. Personally I think they just want to make it a prescription item. More money for the pharmaceuticals and the medical industry. They'd probably make it a schedule II item. That way you'd have to go back to the doctor once a month to get more. Ephedrine is starting to rival Caffeine in popularity.