Could you please explain what the "rear gear back" is? I'm assuming it is the rear landing gear.
ORIGINAL: opjose
15 degrees is excessive, and likely to cause problems.
You only want 2-4 degrees of positive AOA at most.
Bending the rear gear back is not a good idea, as it makes the plane more difficult to rotate.
You need to decrease the length of the rear gear a bit by cutting and bending.