But, I can make an unqualified guess of how to make vit C more tolerable, like making a bone broth soup (or gelatine) salted with potassium chloride. Take the vit C with it. This way the C would be "chelated", brought to the cells by the potassium. Definitely a boost for collagen synthesis; http://www.vitamincfoundation.org/collagen.html
I take my vit c (5-6) grams of ascorbic acid, divided in 3 doses throughout the day; with potassium and magnesium. This way I could double my bowel tolerance, never tested more than 2-3 grams in one go, though.