adding ballast is an ancient method of trimming a boat, whether it be fore/aft or port/starboard. However, I wouldn't do it on a powerboat. You can typically 'shift' weight as needed. If I have a number of people on board, I'll ask some to move down below and forward to assist in getting on plane. I also don't store coolers on teh back deck, those go down below as well. I don't throw everything under the sun into the aft/midcabin either as that contributes to strn loading the weight.
You should have enough ballast lying around the boat which can be redistributed to achieve the same goal. Also consider what your carrying around evey day and whether or not you use it everyday and whether you need it on board. (No you don't use flares, fire extinguishers and life presevers everyday, but you also don't use 10 cans of propane, and bottles of wax, cleaner, a weeks worth of clothes in the lockers, etc.)
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