I've got to say your not adjusting the float correctly. You said fuel was trickling out of the site plug.
You should be able to keep it from coming out the site hole unless you have too much pressure! Its not coming out the vent when you have the plug out right? If its coming out the hole, how do you know its not still rising after you put the plug back in? It could just keep rising to the vent if the seat isn't low enough to let the needle contact it when the float rises(of coarse). No need to put the plug back in until you get fuel to stop coming out the hole.
You are turning the large nut clockwise while holding the slotted screw stationary aren't you? At least I think thats the right direction. Its been awhile.
Sorry if I'm coming across with a little bit of a frustrating tone.