I did do Vit C to bowel tolerance a few weeks ago, and kept it up, then took a week or so off where I went back to a more ordinary lower dose of Vitamin C. You are right that taking it to bowel tolerance did seem to move things along a bit - but it only brought about a bit of runnyness (sorry to be so graphic). I will try it again.
The other tips I have all done to no avail, but the Vit C to bowel tolerance may have more potential, perhaps the small bits of runny output are better than what I'd have without taking that high dose of C, despite being an unhappy compromise that still leaves a person feeling more that is up high in the system just not moving forward.