I would use the "Dynamic Flow Model" of using Vitamin C as outlined by Dr Steve Hickey and Hilary Roberts in their book: Ascorbate: The Science of Vitamin C.
They state that for Vitamin C to be effective, it is not only the dosage, but the frequency of that dosage that is most important. Try 4 Grams at 4 hour intervals for at least 4 weeks to the bowel tolerance level, and couple this with lower doses of the amino acids L-Lysine and L-Proline.