Lot's of good advice here that's all over the map. Michael Smith and Paula Chamlee both use and teach the advantages of a large cloth. Of course they use 8x10 and 8x20 cameras so that might have something to do with it. When I use my 5x7 or 8x10 I go to my BTZS cloth or a large homemade one, with small fishing weighs in it and velco on the sides.
But mostly I shoot with a 4x5 Horseman HD. A very small and light camera with a folding hood on the back. When I do need a darkcloth a small black one the size of a towel works fine, so does a jacket or tee shirt. So, big camera big cloth. Horseman, Linhof or Crown Graphic maybe nothing at all.