Bloat is one of the trickiest medical issues big dogs face. When I first got zoey I spent days reading bloat articles and research, but couldn't come up with a conclusion about what exactly caused it (besides running after eating, that everyone can agree on). For every article I found saying raised bowls help, I found another that said it hurt, etc. (for the record, I feed from raised bowls because zoey has HD and she is much more comfortable standing up straight to eat than trying to bend down)
My official position on bloat became, on the advice of my vet at tufts, to do a preventative tack so I don't always have it hanging over my head. I know that it's not for everyone, but by doing a tack while zoey was spayed, I only added a few days to her recovery time, and yes it was expensive ( a couple hundred dollars extra), but at least now I am not living in fear that we will loose her to bloat.