Answer
We should increase the magnitude of $F_2$
Work Step by Step
Since the bar is stationary, the torque due to $F_1$ must be equal and opposite to the torque due to $F_2$
The torque is a maximum when the angle is $90^{\circ}$
The torque decreases to zero as the angle decreases to zero.
If the angle decreases from $90^{\circ}$, then the torque due to $F_2$ would decrease.
However, to maintain a stationary bar, the torque due to $F_2$ must remain constant.
Therefore, we should increase the magnitude of $F_2$
