Hi David ,
The answer is definitely NO , even with high drag set and moving boat there were time there isn't time to stop big GT from " reefing " you which result in lost lure .
With other species such as tuna , yes you may have time due to no obstructions but with less than 300m in the spool , you want to be very calm when turning that drag knob lest you turn it too much and resulting in torn off or worse line break .
It's best to set the drag prior to your casting the lure , the level of drag set depends on the species n habitat of the fish you are targeting .
Jon .