I believe in FLL method whenever possible. At 42.5 lbs. and $1.59 per concrete block. (That's 25 lbs. under water), about 7 of these blocks with a stainless steel chain looped through them would cost $11.00 plus the chain, shackles, etc, would wind up costing about $50.00 for the whole setup. getting a bigger boat? Add more blocks.