The half blocks will work good for small structure. Even more weight. Be aware of the current in your area if it exists. Using too big of a piece of structure with not enough weight may be moved in a current. The current may only have to be slower than you think to move it. If no current, then bombs away. If there is current, then keep your brush more sparse but use bigger diameter stuff so it will last longer. Just drop more in the area than you would normally do with bigger brush and you will be O.K..CF