Usually when shooting from bags....I use a 10 by 10 piece of scrap leather to save my bag , the flame from the cylinder will destroy your bag if you shoot very much. Also rest the "chin" of the revolver ( the part just ahead of the trigger guard ) on the bag. Then usually my pistol case , which will flatten out like a rug , under my elbows. The inside of my elbow , the bony part , takes a beating when shooting the cannons. With the revolver resting back on the "chin" , I've found I really don't need anything under my wrists. I have put bags under the grip....for me that was a bad idea...my SRH in heavy 454 loadings had no where to slide...it really hammers ya when doing that.....its better with out the grip bag for me. Basically its what suits you and works best for you. Good shooting !
irold