Hi Fishbuster;
I would first suggest talking to people who know Dusky’s as much as people on this board know Seacraft’s. They would have a better insight on your boat.
But if I had to guess and I don’t like guessing not knowing your boat I would think somewhere around where the back of your leaning post seat going forward to somewhere in front of the CC. If the stern of your tank is close to the bilge area of your boat you probably need to move it forward.
I went from a 70” Long 100 gal tank to a 84” long 120 gal tank. I also moved my tank forward approx 12”. By doing this and some other things I redistributed the center balance line of my boat approx 18” forward. So now I usually don’t use my trim tabs for bow to stern trim in average sea conditions I just usually use them for port and starboard listing due to crews beer belly weight and which side of the boat they are standing drinking their suds.
FellowShip
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Just for the Grins
Official 23’ SF Antique Classic SeaCraft Owner