Speed change exponent w.r.t. flow
When the flow multiplier is higher than 1, IceSL
will consider printing tracks wider than the nozzle
width. 
Depending on your printer and material, it may be
necessary to increase the flow multiplier when
printing larger than the nozzle.
This exponent controls the slow down.
For instance, when increasing the flow multiplier:
0.0 => no slow down
1.0 => linear, maintains constant extrusion speed
2.0 => four times slower if extruding twice the width
3.0 => eight times slower if extruding twice the width
When decreasing the flow multiplier, this exponent 
increases the speed instead.
We recommend 3.0 as a safe value.
