Have you ever used a Fiber supplement for your dog with chronic loose stools/diarrhea?

My dog does great on pumpkin but I found a dog food supplement that also provides soluble fiber called "Medi Bulk". I was thinking about giving it a try to help control his VERY sensitive stomach. He gets stools that are really soft, then loose stools and diarrhea. Not . He does not have IBS, pancreatis, or any parasites.