When I began Bowel Tolerance dosing [20 years ago], my Bowel Tolerance was about 10 to 15 grams per day. It has very gradually, but steadily, increased to my current Bowel Tolerance level of 75 to 100 grams daily [divided up into 10 to 15 doses (over the course of the day)]. I believe this has primarily come about because of my ever increasing GI tract health/cleanliness. It has most certainly produced a wonderful health result for me!
As far as "safety" goes, Nick, to quote Dr. Levy, "After over 15 years of researching and personal observation, I can categorically say that high-dose vitamin C is a clinical miracle when compared to all of our modern drugs. Furthermore, volumes of studies exist that say it works. It's one of the safest substances known to man -- we have yet to discover a toxic dose for vitamin C, a bit of a miracle in itself. Even when hundreds of grams have been administered within a few days, the only side effect is good health."