Rampage, the general rule of thumb is 1/3rd the breaking strain of the line you are using, so if using 6lb leader, your drag should be set to around 1kg on a set of scales. That is if you load the rod up the spool on the reel should not be releasing line until such time as you can pull 1kg of force through the loaded rod on the scales you are using.
Whilst I subscribe to the theory, I dont use it. My drag is set by feel. If brawling in the branches, its set tight, if on the flats, I'll fish a little lighter. Its great to have a drag singing its tune, but you just cant let that happen in the sticks.
The stretch in mono / fluro also changes things a bit and helps to compensate for being a little too heavy handed on the drag.
Just make sure that your hooks are up to the job, as the big brawlers will make short work of the lesser quality jobs on the knock down drag em out drag settings required for the structure.