Firefly:
Unless I'm misreading what you are putting the load factor increases as the secant of the angle, not the stall speed. The stall speed is the square root of the load factor.
IE the load factor in a level 60 degree turn is 1/cos60 which is 2. So you are pulling 2g in a level 60 degree turn. The stall speed will increase by the square root of 2 which is 1.414. So if stall speed in level flight is 50kts, youre stall speed in a level 60 banked turn is 70kts.