Tough Question
Kim,Your question is tough for several reasons. First, it's not completely clear to me what you are trying to build. Second, if you are trying to built a hoist to lift your boat from the water, it's so rare that very few can probably answer it. Finally, even if I knew the answer for my boat, it's unlikely to be correct for your boat. Can you trailer to a marina with hoist? They could strap your boat front and rear and do some test lifting. If I were to guess, I'd test the aft cabin bulkhead for the fore-to-aft balance point.