I'm not up on bloat and Vit. C but the study above from Purdue should help. Very interesting to read that a raised food bowl contributes to increased incidence of bloat. I know I've read that some owners think a raised food bowl is good but I don't know why they think that.
I'm so sorry you lost your GSD to bloat. We, thankfully, have had only second hand experience when friends lost dogs. It's pretty awful.