I don't recommend this method on an aluminum frame because it would probably crack and break, but this is what i did on my Steel Frame bike.
On my bike, (steel frame), i had to "stretch" the rear forks apart by hand, about 1/2 an inch to put the rear wheel with sprocket/rotor attached, and then use a spare 15MM axle nut on the sprocket/rotor inside of the drop down, threaded to the axle with blue locktite, to maintain that amount of "stretch" to accommodate the amount of of clearance space the rotor needs so as not to be pressed against the frame.