My 1.6 'tweak' has be limited to rotating the panels in place. I now have the mylar facing away from me and the pole piece is facing me. I feel this has evened out any hi-end stridency, so I don't even think about the resistor in the tweeter and the sweet spot is much larger. I don't know when....or WHY, but Magnepans once were this way, but probably about the time of the QR tweeter, they rotated them to 'mylar front'....
Tweeters on the 'inside' didn't hurt, either, though one day I'll swap 'em side to side and see how tweeter OUT works with the panels rotated......