Davedee, yet another useful reminder from you!

How awful that you have lost your friend in such a way. Yes, as an owner of a Giant Schnauzer, this has crossed my mind too.
http://www.globalspan.net/bloat.htm Have a look, this is in my opinion written very well and clearly.
http://www.vet.purdue.edu/epi/bloat.htm for a scientific study.
As a feeder of raw diet, I am not surprised to learn that cereal-based diets are a risk factor. What also amuses me is that using an elevated bowl actually increases the risk of bloat, and yet so many people swear by these as the miracle prevention of bloat.
Dr. Glickman's (I think) team at Purdue University is the one you want to Google for, should you be interested.
Please note that, based on my rather extensive research into this topic prior to getting a Giant (so I would recognize the symptoms) has shown that an actual physical swelling of the abdomen is rarely present (contrary to what you would expect in "bloat"), and two of the tell tale signs most commonly present are the dog's reluctancy to lie down, especially on its side (the dog may attempt to lie dow, but demonstrate that this is uncomfortable) and the attempt to vomit , without producing anything. The dog may also stretch its chin upwards, as if trying to stretch its throat. In the more advanced stage of bloat, a normal gurgling (digesting) sound from the abdomen can't be heard, as the stomach has flipped over, and as it fills with gas, swelling may or may not be visible to the naked eye. But the trouble is, as with pyo, that there are no fixed symptoms and symptoms can vary from case to case, so it can really be just down to the owner's gut feeling. (no pun intended)
You can also find on the net some info regarding first aid for bloat (if a vet can't be reached within minutes), which involves inserting a tube down the dog's throat (although how this works when the stomach has rotated, I don't know) or in a real emergency, owner's hand. You might want to get some professional guidance into this, before you go experimenting, though.
If you think your dog may have bloat, and your vet tells you otherwise, kick up a huge fuss and demand they do something NOW! My friend's Alsatian would be dead now, had his owner believed the first vet. She argued that this is not normal "upset tummy" for her dog and demanded to see a more senior vet, who diagnosed bloat and operated immediately- by which time the dog was drifting in an out of consciousness and had to be resuscitated on the operating table as the heart gave in. (and I think the owner needed sedation too!

) The dogwas one of the lucky ones and made it, but only just. You know what is normal for your dog, so if you think your best friend is in danger, then he probably is.
As Davedee said, if you think something is not right, you must have the dog at the vet's within minutes- "wait and see", as they often tell you on the phone, will result in a dead dog.
*Soph is getting down from her soap box*
ps. I wonder if the standard is the same around the country, but we have such excellent vet care around here, they will see you in an emergency within 15 minutes, day or night, and my friend's Yorkie received an emergency operation quite literally in the middle of the night! How many of you remembered to send a Christmas card to you vet from your pet? Am I really sad if I did? :D