With that particular tackle it's unlikely you can actually load it by hand to beyond your limits... if you don't put it on a winch I don't think you can ever get too much load on it.
So I think you can play with your adjustment to your heart's content. As Steve says above, observe the effects and figure out what actually works.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)