The drag on a reel is probably the most mis understood, abused item in most aglers arsenal... buy the scale..a quality brass 50lb scale is cheaper then a spool full of power pro...
The drag on a reel is simply a brake... but goes through several stages in a battle...
1) starting drag... this is what you are actualy setting, it SHOULD be set for 1/4 the breaking strength of the WEAKEST part of your line/leader connection... if your using 50lb PP but run a 20lb leader, the correct drag setting would be 5 lbs...this should be set with a "fighting" curve in the rod, somewhere in the vicinity of 10:00..
2) running drag, this is the amount of friction available as the spool has been set in motion, in the beginning it will be consideably less than the starting drag, if the fish takes a long run, it increases as the diameter of the spool shrinks and the resistance of the water adds up on the line, older, un cared for drags may become jerky and un smoothe.. the 1/4 ratio gives you a cushion to cover a wide spectrum including unseen knicks .cuts and poor kmnots... extra drag can be applied ( lightly) with a finger or palm... better to err on the side of caution, if I had a dollar for every angler that fished a drag that was too tight.. I'd retire right now and go fishing In some warm climate...
the exceptions: and there are quite a few, I'll name a few...
Rock piles and pilings.... guy's( and gals) that frequently fish these places have little choice but to use heavy lines and tight drags, if they dont they sacrafice fish to the rock gods ( no relation)
Fast water... Cape cod canal is one of these places... if the drag is not 1/3 -1/2.. and the tackle heavy... good chance the fish is gone...they just point their nose with the current and head with it...
so why not fish a tight drag all the time.. simple.. tight drags loose fish and break tackle.. it's as simple as that... hooks pull or bend, rods and guides break... gears get stripped in reels.
in summary: use a spring scale.. maintian your drags "health" by loosening the drag after each trip and keeping sand out of it... set it to 1/4 the breaking strength ( unless you have no choice) of the weakest link... and go fishin'!
tight lines
Roc