just my opinion but that is about as big a chunk as i would want to put in mine but I would probably only use 2 at a time. I usually use chunks that are between the size of a large orange and a grapefruit and typically use 2 chunks every 3-4 hours or so. When the pieces are too big its hard to squeeze them under the water pan and onto the hot coals without really agitating your fire.
I just buy the bags they sell at Lowes or Home Depot and most of the stuff in them is between a golf ball and a baseball in size.
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