oh, okay... what I would think was that position 1 is the neck pup, 3 the middle and 5 the bridge.

so what I was thinking as I read that would make sense: when just one pup is selected, notes would naturally feedback, because there arnt any other pups to even it out. when its at positions 2 and 4, more than one pup is selected, which would allow somewhat of a humbucker effect- that some of the feedback is reduced.

but you are saying 4 feedsback alot for you, and 5 doesnt. which doesnt seem right to me. did you switch the numbers accidentally?