Back when I was flying the 206, our company limited it to 80% TQ max continuous, and that's what we usually flew at. We just pulled 80% TQ and accepted whatever airspeed we got. 80 kts isn't close to the maximum airspeed you can get if you pull the torque up into the yellow, it's just the maximum allowed to prevent excessive mast bending. You pull whatever torque it takes to take off (almost always > 90%, very often 99% in the GOM at max weight), then reduce to 80% as your airspeed increases and fly away. If you keep the torque up, you'll exceed 80 kts fairly quickly.