a 3" lift on stock arms and struts will definatly throw the camber out (positive), as you all know and seen already.
flipping the strut mount will have no change in the camber settings, unless you slot the strut holes and move the top of the strut in towards the centre of the car.
i have found that sometimes slotting the upper strut-to-knuckle hole does not allow for enough camber change, as the knuckle hits the strut body. if you do slot the upper hole, do it so it moves the top of the knuckle inwards.
or you can slot the lower hole and pull the bottom of the knuckle outwards. this also will help the camber a bit better. by doing the lower hole, there seems to be more room out than in.
if it still does not work, you can do both.
another way if you cant get a hole of some descent camber bolts, is to run smaller bolts through the holes as well, but you will need larger washers on either side.
the hagen widening mod moves the lower arms outwards, hence widening. this will push the lower ball joint on the lower a arm OUT, and will push the bottom of the tyres out. which is what you want. slotting the lower strut holes is similar to this, only not as big or a change.